A site

A site on the ribosome occupied by aminoacyl-tRNA.

11

ABC transport systems

A type of active transport including several proteins and several steps in which the molecule being transported is handed off from one protein to the next.

9

Abscess

A lesion that contains pus in a cavity hollowed out by tissue damage.

26

Acidophiles

Organisms that grow best in an environment with a pH of 4.0 to 5.4.

10

Active agglutination

Type of agglutination where the antigen occurs naturally on a particle.

6

Active immunization

An immunization in which antigen representing the infectious agent is administered and confers immunity. This is used to increase herd immunity.

13

Active site

The location on an enzyme where reactants are made into products.

3

Active transport

The mechanism used to transport things from one side of a membrane to the other in a process that requires ATP.

9

Active viremia

Viruses replicating in the blood.

13

Acute congestion

A phenomenon that occurs where local capillaries become engorged with neutrophils.

21

Acute croup

Also known as laryngotracheitis. A severe infection of the larynx and trachea.

21

Acute disease

The opposite of chronic disease; one in which infection occurs quickly and lasts a short time.

7

Acute inflammatory colitis

Rapid inflammation of the colon.

22

Acute influenzal syndrome

An acute influenza in which symptoms can develop in a matter of hours.

21

Acute pancreatitis

The rapid onset of serious inflammation of the pancreas.

14

Acute phase of HIV infection

This phase occurs in the first few days after initial infection: the virus is reproducing in the lymphocytes of the lymph nodes, resulting in lymphadenopathy and flu like symptoms.

17

Acute-phase protein

A protein such as C-reactive protein or mannose-binding protein that is related to the development of the inflammatory response but is seen only in acutely ill patients.

15

Acute septic shock

The rapid onset of hypotension associated with overwhelming infection. It is thought to result from the action of endotoxins.

7

Acute urticaria

Sudden onset of vascular reactions in the upper dermis marked by transient appearance of slightly elevated patches that are redder than the surrounding tissue.

17

Acyclovir

An antibiotic used for viral infection. Acyclovir is a synthetic purine nucleoside with activity against herpes simplex virus.

19

Adaptive immune response

A specific host defense composed of the humoral (antibody) and cellular immune responses. It has memory and takes several days to get started.

1

Adhesin

A protein or glycoprotein found on attachment pili or in capsules that helps microorganisms attach to host cells.

5

Aerobe

An organism that uses oxygen.

10

Aerobic respiration

Metabolism that uses oxygen as the final electron acceptor.

3

Aerotolerant bacteria

Bacteria that grow in the presence of oxygen but do not use oxygen for metabolism.

10

African trypanosomiasis

A neurological disease caused by the parasite Trypanosoma otherwise known as African sleeping sickness.

14

Agar

A low-melting-point complex polysaccharide derived from marine algae and used to solidify media for the growth of microorganisms.

10

AIDS (acquired immune deficiency syndrome)

A viral infection caused by the human immunodeficiency virus (HIV), which destroys a patient’s helper T cells and thereby his or her adaptive immune response.

1

AIDS dementia

A metabolic encephalopathy induced by HIV infection manifested by cognitive, behavioral, and motor abnormalities.

17

Alcoholic fermentation

Fermentation in which pyruvic acid is reduced to ethanol.

3

Alkaline phosphatase

Enzyme that catalyzes the removal of phosphate groups from molecules.

6

Allergen

An ordinarily innocuous foreign substance that can elicit an adverse immunological response in a sensitized individual.

17

Allergic asthma

Recurrent attacks of difficulty in breathing and wheezing due to spasmodic contractions of the bronchi.

17

Allergic conjunctivitis

Inflammation of the conjunctiva caused by allergic reaction and characterized by itching, tearing, and redness.

17

Allergic reaction

Also called hypersensitivity. It is a disorder in which the immune system reacts to antigens that it would normally ignore.

17

Allergic rhinitis

Allergic reaction of the nasal mucosa.

17

Allolactose

A fragment of the sugar lactose that acts as an inducer molecule and allows the lactose operon to be turned on.

11

Allosteric inhibition

Also known as the allosteric effect. It involves the binding of a non-competitive inhibitor to a site on the enzyme molecule that causes a change in the shape of the active site and inhibits the binding of the substrate in the active site.

3

Alpha hemolysis

Partial lysis of red blood cells, leaving a greenish ring in the blood agar medium around the colonies.

10

Alternative pathway of complement

One of the sequences of reactions seen in the complement system of innate immune response initiated by factors B, D, or P.

15

Alveolar macrophage

A macrophage that is found in the alveoli of the lungs.

15

Amantadine

An antiviral agent that prevents the penetration of host cells by the influenza virus.

19

Amastigote

The intracellular morphologic stage in the development of certain hemoflagellates.

25

Amebiasis

Infection with ameboid protozoan parasites, in particular Entamoeba histolytica.

14

Amebic dysentery

A gastrointestinal infection characterized by bloody diarrhea, caused by Entamoeba histolytica.

22

Ameboids

Cells that move or change shape by means of protoplasmic flow.

14

American trypanosomiasis

The American form of trypanosomiasis, also known as Chagas' disease.

14

Aminoacyl-tRNA synthetase

The enzyme required for binding the amino acid to the transfer RNA molecule.

11

Aminoglycoside antibiotics

Chemical agents that block bacterial protein synthesis.

19

Amphitrichous flagella

One of the four forms of flagellar arrangement. In this case there are flagella at both ends of the bacterial cell.

9

Anabolic

Relating to anabolism, the creation of large molecules from small molecules.

3

Anabolism

Chemical reactions in which energy is used to synthesize large molecules by using smaller molecules (this process involves synthesis reactions).

3

Anaerobic respiration

Metabolism that takes place without oxygen. In this case the final electron acceptor is an inorganic molecule other than oxygen.

3

Analytical epidemiology

A form of bioinformatics that focuses on establishing the cause-and-effect relationship and can use prospective or retrospective data.

6

Anaphylactic shock

Condition resulting from a sudden extreme decrease in blood pressure due to an allergic reaction.

17

Anaphylaxis

An immediate exaggerated allergic response to antigens.

17

Anergy

Automatic inactivation of a lymphocyte due to lack of co-stimulation.

16

Angiogenesis

Development of blood vessels.

15

Animal virus

A virus that infects animal cells. Human cells are considered animal for this definition.

12

Anion

A negatively charged ion.

2

Anthrax

A fatal disease of ruminants contracted by humans through contact with contaminated wool or animal products, or inhalation of spores.

1

Anthrax toxin

A powerful cytotoxin produced by Bacillus anthracis, which increases vascular permeability. It has three components: edema factor, protective antigen, and lethal factor.

5

Antibiotics

Chemicals that are taken internally to control the growth of microorganisms in a host.

1

Antibody

Also known as an immunoglobulin. A class of proteins that are produced by the humoral immune response and respond to a specific antigen.

6

Antibody titer

The quantity of antibody found in serum.

16

Anticodon loop

A portion of the transfer RNA molecule that associates with the codon of the messenger RNA molecule at the ribosome.

11

Antigen

Also known as an immunogen. Any molecule that will elicit an immune response.

6

Antigen binding site

The site on the antibody molecule that interacts with epitopes on the antigen. It is made up of a portion of the variable region of the heavy chain and a portion of the variable region of the light chain.

16

Antigen-presenting cell

A cell that processes antigens and places them on their surface for presentation to helper T cells. The predominant ones are macrophages or dendritic cells, but the B cell can also present antigen.

16

Antigenic drift

The process of antigenic variation that results from mutations.

13

Antigenic shift

The process of antigenic variation caused by the re-assortment of genes.

13

Antigenic variation

Mechanisms by which pathogens change their antigenic surface proteins in order to evade the adaptive immune system.

9

Antimicrobial

An agent that will inhibit the growth of a microbial organism.

18

Antisepsis

The application of an antimicrobial agent to living tissue or skin.

18

Antiseptic

A chemical substance that can be used on tissues to control the growth of microorganisms.

1

Antiviral proteins

Proteins produced through stimulation by interferon that become active in the presence of double-stranded RNA and can protect cells from being infected with virus.

15

Apoptosis

Genetically programmed cell death; a process in which the cell commits a kind of suicide. This occurs when cells are worn out or if specific signals are given to the cell, as in cytotoxic reactions.

15

Arbovirus

A group of viruses that are transmitted to humans by mosquitoes or ticks, including agents of yellow fever and viral encephalitis.

25

Arthroconidia (singular arthroconidium)

Specialized stalk stuctures that hold conidia found in some fungi.

14

Arthus reaction

A localized inflammatory response with increased vascular permeability at the site.

17

Aseptic

The use of techniques that minimize the chances of cultures becoming contaminated.

18

Asian influenza

The term used to describe an influenza pandemic that occurred in 1957 and caused more than 70,000 deaths in the United States.

8

Aspergillosis

Disease caused by Aspergillus fungi which causes the development of inflammatory granulomatous lesions in the skin, nasal passages, lungs, bones, and meninges.

14

Ataxia

Lack of voluntary coordination of muscle movements.

13

Ataxia telangiectasia

Primary immunodeficiency syndrome involving reduced numbers of T cells.

17

Atopy

Hypersensitivity to environmental allergens.

17

ATP

The biological energy molecule consisting of adenosine coupled with three phosphate atoms. Breaking the third phosphate off releases energy and ADP, that can be converted back to ATP with the addition of a phosphate and energy.

2

Atrichous

The condition of nonmotile bacteria, in which flagella are absent.

9

Autoclave

An instrument for sterilizing by means of moist heat and pressure.

18

Autotrophy

Obtaining carbon atoms from CO2.

3

Avian influenza

Also known as bird flu. A type of influenza seen in avian species that has been able to infect humans. It is similar to the influenza virus that caused the Spanish flu pandemic of 1918.

8

Axial filament

Also known as an endoflagellum. It is a subsurface filament found in spirochete organisms that causes the spirochete to rotate in a corkscrew fashion.

9

Axostyle

A microtubule used for attachment and tissue damage found on the parasite Trichomonas vaginalis.

14

β-lactam antibiotics

Any natural or semisynthetic antibiotic containing a β lactam ring structure.

19

β-lactamase

An enzyme produced by penicillin-resistant bacteria that destroys the β-lactam ring of penicillin.

19

B cell (B lymphocyte)

A lymphocyte that is part of the adaptive immune response. This cell is formed in the bone marrow and matures there; it is responsible for the humoral (antibody) response of the adaptive response and differentiates into a plasma cell which produces antibody.

16

B-cell lymphoma

Non-Hodgkin’s form of neoplasm seen in lymphoid tissue.

17

Bacillary dysentery

A gastrointestinal infection characterized by bloody diarrhea, caused by Shigella organisms.

22

Bacillus (plural bacilli)

A rod-shaped bacterium.

4

Bacitracin

An antibacterial polypeptide produced by Bacillus subtilis that prevents cell wall synthesis.

19

Bacteremia

Bacteria in the bloodstream.

7

Bacterial hemorrhagic disease

Loss of blood from vessels caused by certain bacterial species.

1

Bacteriocidal

Term describing an agent that kills bacteria.

18

Bacteriocins

Antimicrobial peptides with narrow or broad host ranges produced by bacteria. They have no effect on the organism producing them.

7

Bacteriophage

Viruses that infect bacteria.

11

Bacteriostatic

Term used for chemicals that inhibit microbial growth but do not kill the organisms.

18

Bacteriuria

Bacteria in the urine.

23

BALT

Bronchius-associated lymphoid tissue.

16

Basophil

A type of white blood cell containing large numbers of granules. This cell releases histamine and other molecules as part of the inflammatory response.

15

Bed sore

A decubitus ulcer on the skin.

6

Beta hemolysis

Complete destruction of red blood cells by bacterial enzymes.

10

Betadine

An iodophor routinely used to prepare human skin for surgery and injection.

18

Binary fission

The process in which a bacterial cell duplicates its components and divides into two identical daughter cells.

5

Biofilm

A structure composed of a variety of bacterial species that coexist. It is often seen as the beginning layer of plaque, which builds up on teeth.

4

Biosensors

Analytical tool using a biological component in the detection principle.

6

Biotechnology

An industry that uses molecular biology and microorganisms for specialized purposes, including genetic engineering.

6

Bioterrorism

The use of microorganisms as weapons.

8

Bioweapon

A harmful biological agent that is used as a weapon.

8

Bisphenolics

Chemical disinfectants consisting of two covalently linked phenolic compounds.

18

Black death

Also known as pneumonic plague. An infection of the lungs with Yersinia pestis, causing a highly contagious form of plague.

4

Blastoconidia

The products of the budding form of reproduction seen in fungi.

14

Blood agar

Bacterial growth medium that contains blood; used to identify organisms that produce hemolysins, which break down red blood cells.

10

Blood-brain barrier

A selectively permeable barrier separating the circulating blood from the cerebrospinal fluid of the brain.

24

Boil

A massive pus-filled lesion resulting from an infection in which the invading pathogens have been walled off. It is usually seen in the neck and back.

5

Botulinum toxin

A neurotoxin associated with botulism, a digestive intoxication resulting from food poisoning.

5

Broad spectrum antibiotics

Chemicals that attack a wide variety of microorganisms.

19

Bronchitis

Acute or chronic inflammation of one or more of the bronchi.

21

Broth dilution test

A test used to determine the minimal microbicidal concentration.

20

Bubo

Enlargement of infected lymph nodes, especially in the groin and armpit, due to the accumulation of pus. This is seen in bubonic plague and other diseases.

25

Bubonic plague

A noncontagious form of plague caused by Yersinia pestis and transmitted to humans by the bite of a flea. It is a systemic disease that spreads through the blood and lymph fluid. Spread of the infection to the lungs causes the highly contagious form of plague known as pneumonic plague or black death.

25

Cadherin

A transmembrane protein that has a role in cell adhesion.

5

Candidiasis

A yeast infection caused by Candida albicans. It can appear as thrush in the oral cavity or as vulvovaginitis.

23

Cannula (plural cannulas)

A tube with a retractable inner core to be inserted into a blood vessel or other body cavity.

5

Capsid

A protein outer coat of a virus. It is made up of repeating protein subunits known as capsomeres.

12

Capsomere

A protein subunit that, along with other identical subunits, makes up the capsid (protein coat) of a virus.

12

Capsule

A protective structure found around the outside of a bacterial cell. It can be made up of polysaccharides, polypeptides, or a combination of both.

4

Carbapenem antibiotics

Antibiotics that attack the cell wall of bacteria.

19

Carbon source

Compound that is used by an organism to source carbon from to be integrated in the organism's biomass.

6

Carbuncle

A massive pus-filled lesion resulting from an infection in which the invading pathogens have been walled off. It is usually seen in the neck and back.

26

Carrier molecule

Usually a co-factor or coenzyme used in metabolic pathways.

3

Catabolic

Relating to catabolism, the breakdown of large molecules into smaller molecules.

3

Catabolism

The chemical breakdown of organic molecules in which there is a release of energy.

3

Catalase

An enzyme that converts hydrogen peroxide to water and oxygen.

10

Catalyst

A molecule that speeds up a chemical reaction but is not used up or changed in the process.

3

Cation

A positively charged ion.

2

Cell line

A population of cells from a multicellular organism that are kept in culture media and used for research.

13

Cellular immunity

Part of the adaptive immune response. It comprises the activity of T cells in response to antigens.

16

Central tolerance

A part of clonal selection where newly formed lymphocytes that react with self antigens are eliminated.

16

Cephalosporin family

A group of antibiotics derived from the fungus Cephalosporium. These chemicals attack the cell wall of bacteria.

19

Cercaria

A tail-bearing larval form of trematodes.

14

Cervicitis

Infection of the cervix.

23

Cestode

A tapeworm.

14

Cestodiasis

Infection with parasitic flatworms (cestodes).

14

Chagas’ disease

The American form of trypanosomiasis.

14

Chagoma

A local chancre associated with Chagas’ disease, filled with neutrophils, lymphocytes, and tissue fluids.

25

Chancre

An ulcer located on the external genitalia or cervix seen in cases of syphilis.

23

Chediak – Higashi syndrome

Primary immunodeficiency disease leading to lethal progressive systemic disorders and recurrent or chronic bacterial infections.

17

Chemical agent

A general term that includes both antiseptics and disinfectants.

18

Chemically defined growth medium

Growth medium in which each of the ingredients is precisely defined.

10

Chemiosmosis

The process of capturing energy in which a proton gradient is created in the electron transport chain and is used to provide energy for the formation of ATP.

3

Chemoautotroph

An autotroph that obtains energy by oxidizing inorganic substances such as nitrites and sulfides.

3

Chemoheterotroph

Organism that obtains energy from breaking down already-formed organic molecules.

3

Chemokine

A class of cytokines that attract additional phagocytes to the site of infection.

8

Chemostat

A device used to maintain the logarithmic growth of bacteria by the continuous addition of fresh growth medium.

10

Chemotaxis

A nonrandom movement of an organism toward or away from a chemical.

15

Chickenpox

A highly contagious disease characterized by skin lesions and caused by the varicella-zoster virus. It is usually seen in children.

7

Chloramines

Combinations of chlorine and ammonia used in wound dressings.

18

Chocolate agar

Type of medium made with heated blood and used for growing organisms that require heme for growth.

10

Cholera

An acute infectious disease caused by Vibrio cholerae. It causes severe diarrhea with extreme fluid and electrolyte depletion.

5

Cholera toxin

An exotoxin produced by Vibrio cholerae pathogens. It is an enterotoxin that causes increased permeability in the intestinal tract and a consequent loss of fluids.

5

Chromatin

The form of DNA seen in cells that are not ready to divide. It has the appearance of threads.

4

Chromosome

The structure containing DNA that is seen in cells that are ready to divide. It is derived from the condensation of chromatin.

4

Chronic disease

The opposite of acute disease. Such a disease starts slowly and lasts a long time.

7

Chronic granulomatous disease

Primary immunodeficiency disease causing frequent severe infections of the skin, oral mucosa, intestinal tract, bones, lungs, and genitourinary tract.

17

Chronic infection

A type of persistent infection in which there is continuous and long-term production of virions.

13

Cilia (singular cilium)

Short cellular projections seen in eukaryotic cells, used for movement that result from the beating of these projections in coordinated waves.

4

Ciliates

Organisms that move by the use of cilia; they are rarely parasitic to humans.

14

Circulatory shock

The profound hemodynamic disturbance caused by the failure of the circulatory system to maintain adequate perfusion of organs.

8

Cirrhosis

A general term for a group of liver diseases marked by interstitial inflammation and fibrosis of the liver.

22

Class I MHC

A group of cell-surface proteins that are essential to immune recognition reactions. Class I MHC molecules are involved in natural killing functions and are found on all cells except those involved in the adaptive immune response.

16

Class II MHC

A group of proteins found only on the surface of cells, involved in the adaptive immune response. These proteins are absent until an immune response is generated and they have an important role in antigen presentation.

16

Classical pathway of complement

One of the ways in which the innate immune response works to protect the body. This pathway responds to antigens that have been seen previously and involves antibody against those antigens.

15

Clinical latency

The effect seen in HIV infections in which virus replication is very low and is mainly in the lymph nodes.

17

Clinical trial

A research study that uses human participants in health-related interventions to evaluate the effects of e.g. a new drug or vaccine on the health outcomes.

6

Coccodiomycosis

Disease caused by members of the genus Coccidioides.

14

Clonal selection

A theory that explains how exposure to an antigen selects and stimulates a specific lymphocyte to proliferate, giving rise to a clone of identical responsive cells.

16

Clonorchiasis

Infection of the biliary passages of the liver by the liver fluke Clonorchis sinensis.

14

Coccus (plural cocci)

A spherical bacterium.

4

Codon

A sequence of three bases in messenger RNA that code for a particular amino acid.

11

Coenzyme

An organic molecule bound to or associated with an enzyme.

3

Cofactor

(1) An inorganic ion required for the function of an enzyme. (2) A component necessary for viral attachment to the host cell.

3

Cold sore

A lesion caused by herpes simplex type 1 virus that is usually found on the lips or gingiva of the oral cavity.

13

Colony morphology

The physical appearance (e.g. color, shape) of a bacterial colony.

6

Commensalism

A symbiotic relationship in which one organism benefits and the other is unaffected.

7

Common-source outbreak

An outbreak arising from contact with contaminated substances such as water.

6

Communicable disease

An infection that can be spread from person to person.

7

Competitive inhibition

A reaction in which a molecule that is similar in structure to a substance competes with that substance by binding to the active site of an enzyme.

3

Complement protein

Serum protein that is part of the innate immune response.

5

Complement system

A set of more than 20 proteins found in the blood that when activated can destroy bacteria by making holes in the bacterial cell wall. This system also amplifies the inflammatory response to infection.

15

Complete blood count (CBC)

A laboratory procedure in which the formed elements (cells) of the blood are counted. This information can be of great value in determining the stage of infection seen in a patient.

15

Complex growth medium

A growth medium that contains ingredients such as beef extract or blood, whose exact composition is not known.

10

Complex viruses

Viruses without either helical or icosahedral symmetry.

12

Concentration gradient

A condition in which the amount of a substance differs between locations, for example, between the two sides of a membrane.

3

Condyloma

Also known as a genital wart. It is an often malignant lesion that arises on the genitalia and is usually associated with sexually transmitted viral diseases.

8

Congenital syphilis

Syphilis that is present at birth. It occurs when a child is born to a mother with syphilis.

23

Conidia

The asexual reproductive elements found in fungi.

14

Conjugation

The transfer of genetic information from one bacterial cell to another. In Gram-negative bacteria this occurs through the use of a pilus, whereas in Gram-positive cells it occurs when two cells stick together.

11

Conjunctivitis

An infection of the conjunctiva of the eye.

26

Constant region of the antibody molecule

The part of the immunoglobulin molecule with a relatively constant amino acid sequence. It determines the effector function of the immunoglobulin molecule.

16

Constitutive gene

A gene that is always turned on, in contrast with inducible or repressible genes.

11

Contact transmission

A mode of disease transmission; it can be direct, indirect, or through droplets.

6

Contagious

A disease that is communicable on contact and spreads quickly.

7

Continuous cell line

A cell line that grows for long periods of time or indefinitely.

13

Co-stimulatory signal

A signal generated from, and regulated by, cells of the innate immune system.

16

Covalent bond

A bond between atoms in which electrons are shared.

2

C-reactive protein (CRP)

An acute-phase protein that binds to phospholipids and is seen in acute infections.

15

Croup

Acute obstruction of the larynx that causes a hoarseness and barking cough.

21

Cryptosporidiosis

Disease caused by protozoans of the genus Cryptosporidium, commonly seen in patients who are immunocompromised.

8

Cultures

Term used for microorganisms grown on purpose e.g. in the laboratory.

6

Cutaneous anthrax

Infection with Bacillus anthracis that appears on the skin two to five days after endospores enter the epithelial layers of the skin.

26

Cutaneous candidiasis

A fungal infection of the skin caused by Candida albicans.

26

Cutaneous leishmaniasis

An infection of the skin caused by the parasitic protozoan Leishmania and transmitted to humans by the bite of a sand flea.

26

Cyanosis

Bluish discoloration of the skin and mucous membranes caused by a lack of oxygen in the blood.

21

Cyst

A spherical thick-walled structure that resembles an endospore; formed by certain parasites.

14

Cysticercus

An embedded form of tapeworm found in meat, giving the meat a “mealy” appearance.

14

Cystitis

Infection of the bladder.

23

Cytocidal effect

Part of the pathology seen when host defenses kill virally infected cells.

5

Cytokines

Low-molecular-weight proteins that are released by a variety of cells in the body. There are two types: the hematopoietin family, which includes growth hormones and interleukins, and the tumor necrosis factor family.

8

Cytomegalovirus (CMV)

One of a widespread and diverse group of herpesviruses that often produce severe effects in immunodeficient patients.

25

Cytopathic effect (CPE)

The destruction of host cells through the lytic cycle of viruses.

5

Cytoplasm

The semifluid substance inside cells, excluding the nucleus of eukaryotic cells.

4

Cytoskeletal structures

Structures found inside cells made up of protein fibers that give rigidity and support to eukaryotic cells and permit cell movement.

9

Cytotoxic chemotherapy

The use of cytotoxic drugs to kill malignant cells or depress the immune system to allow the survival of transplants. These drugs cause leucopenia, which is a decrease in the number of white blood cells.

6

Cytotoxic edema

Swelling in the brain caused by the production of toxic substances by bacteria and from neutrophil invasion.

24

Cytotoxic T cell (CTL)

A specific thymus-derived T lymphocyte that kills other cells and has memory.

16

Cytotoxins

Toxins produced by cytotoxic cells that kill infected host cells.

5

Dacryocystis

Infection of the tear ducts.

26

Death phase

Also known as logarithmic decline phase. The fourth phase of bacterial growth, in which bacteria die faster than they divide.

10

Deep sequencing

Nucleotide sequence analysis with increased scale of readings of parts of the sequence to increase accuracy of the reconstructed sequence.

6

Defensins

Antibacterial peptides produced by humans.

20

Definitive host

An organism that harbors the adult sexually reproducing form of a parasite.

14

Degenerate genetic code

The genetic code is said to be degenerate because more than one codon can code for the same amino acid. This allows for mistakes that can take place in the DNA sequence: the appropriate amino acid can still be placed in the primary protein sequence.

11

Degerming

The method of moving organisms away from a place on the body; an example is the application of alchohol before injections.

18

Dehydration synthesis

A chemical reaction in which water is removed so as to build a complex organic molecule.

2

Dendritic cell

A phagocytic cell found in the dermis; responsible for antigen presentation to helper T cells in the adaptive immune response.

15

Deoxyribose

The sugar found in DNA.

11

Dermatophytosis

The general term for a variety of dermatophyte infections involving erythremia, induration, itching, and scaling.

26

Descriptive epidemiology

The study of the physical aspects of patients and the spread of disease.

6

Detergents

Positively charged organic surfactants that are more soluble in water than soap.

18

Diapedesis

The process by which white blood cells move through unbroken capillary walls to the site of an infection.

15

Diarrhea

Abnormally frequent evacuation of watery feces.

1

Diarrheagenic

Causing diarrhea.

22

Differential blood analysis

A routine lab test in which the percentage of each of the white blood cell populations is determined.

15

Differential media

A growth medium that includes components that cause an observable change in color or pH when a particular chemical reaction occurs, making it possible to distinguish between organisms.

6

Differential stain

The use of two or more dyes to differentiate between bacterial species or distinguish different structures of an organism.

4

DiGeorge syndrome

Primary immune deficiency disease in which the thymus does not develop properly, causing a deficiency of T-cell functions.

17

Dimorphism

The term used to describe the ability of some fungi to grow in either the mold or the yeast form.

14

Diphtheria

An acute bacterial infection of the nose, throat, or larynx caused by Corynebacterium diphtheriae. It is marked by formation of a grey/white pseudomembrane.

4

Diphtheria toxin

An exotoxin produced by Corynebacterium diphtheriae that affects the membranes of the nose, throat, and larynx. It can also affect the heart and the central nervous system.

5

Diplococcus  (plural diplococci)

The arrangement of bacteria that grow in pairs. Streptococcus pneumoniae, the leading cause of pneumonia, is an important example.

4

Direct method

A measurement of bacterial growth in which cells or colonies are observed.

10

Directly observed therapy (DOT)

Observation of the patient taking the prescribed medication by a health care worker to ensure compliance with the medication schedule.

21

Disease

A negative disturbance in the state of health during which the body does not function properly.

7

Disinfectants

Chemical agents used on inanimate objects to destroy microorganisms.

1

Disinfection

The application of an antimicrobial agent to inert surfaces, such as floors or tabletops.

18

Disk diffusion method

Used to test the efficacy of an antimicrobial chemical. The chemical is applied to a small filter paper disk and placed on a bacteria-inoculated petri plate, to determine how well it inhibits bacterial growth.

18

Disseminated

Spread throughout an organ or the body.

13

Disseminated intravascular coagulation (DIC)

Widespread coagulation of the blood in different areas of the body.

5

Dissimilation plasmid

An extrachromosomal piece of genetic material that contains genes that enable organisms to be resistant to disinfectants and environmental pressure.

11

Distending cytotoxin

A toxin produced by Campylobacter that arrests cell division while the cytoplasm continues to increase.

22

Disulfide bridge

A bond that forms between sulfur-containing amino acids. It is one of the primary ways in which the three-dimensional folded shapes of proteins are maintained.

2

Diverticular abscess 

A pus-containing lesion occurring in the diverticulum of the intestinal tract.

22

DNA ligase

An enzyme that is used to connect sections (fragments) of DNA together by filling in gaps. It is seen on the lagging strand of DNA during replication.

11

DNA polymerase

The enzyme used to match and bond complementary base pairs during the process of DNA replication.

11

Double-stranded DNA (dsDNA) virus

A virus that possesses two complementary strands of DNA.

12

Dry heat

Hot air with a low moisture content. For example, in an oven.

18

Dual immunological response

A vaccine response in which both specific antibodies and T cells are produced within the vaccinated host.

13

Dysentery

A severe diarrhea in which the fecal material contains mucus and blood.

5

Dyspnea

Labored or difficult breathing.

21

Dysuria

Pain and burning sensations during urination.

14

E site

A site on the ribosome where the tRNA exits after the removal of its amino acid.

11

E test

A diffusion method used to determine the MIC (minimal inhibitory concentration) of a drug.

20

Eastern equine encephalitis (EEE)

Type of viral encephalitis seen most often in the eastern United States; it primarily infects horses but can also infect humans.

24

Ecchymosis (plural ecchymoses)

A small hemorrhagic spot in the skin or mucous membranes forming a nonelevated irregular blue or purplish patch.

8

Effector lymphocytes

Activated lymphocytes that have differentiated into their fully effective form.

16

Efflux pumping

A mechanism used by bacteria to resist attack by antibiotics. It takes advantage of pumps in the plasma membrane that pump out the antibiotics.

9

Elective media

Growth media that include components that only support growth of the organism of interest.

6

Elementary body

The infectious form of Chlamydia.

23

Elephantiasis

Swelling of the extremities and genitalia as a result of an intense inflammatory response and lymphatic blockade by the parasite Wuchereria bancrofti.

25

Embolus  (plural emboli)

A mass of clotted blood or other material that is brought by the blood and forced into a smaller vessel, obstructing the circulation.

25

Emerging infectious disease

Diseases that have not been seen before. They arise from movement into areas where humans have not ventured before. They can also be diseases that move from certain areas of the world to places where the diseases have not been before.

8

Encephalitis

Inflammation of the brain.

8

Endemic disease

Refers to a disease that is constantly present in the population.

6

Endemic typhus

A flea-borne typhus caused by Rickettsia typhi.

25

Endoarteritis

Inflammatory lesions that occur in the arteries.

25

Endocarditis

Exudative and proliferative inflammatory lesions found on the endocardium and valves of the heart.

25

Endocytosis

The process in which vesicles form by invagination of the plasma membrane of the cell and move substances into the cell.

4

Endogenous infection

An infection caused by organisms that are part of the normal microbial flora of the body.

22

Endometritis

Infection of the endometrium.

23

Endoplasmic reticulum

An extensive network of membranes that form tubes and plates in the cytoplasm of eukaryotic cells. They are involved in the synthesis and transport of proteins and lipids.

4

Endosome

A membrane enclosure seen during the virus penetration step of the infection process.

12

Endospore

A highly resistant dormant structure that is formed by certain bacteria.

4

Endosymbiotic theory

Evolutionary theory holding that the organelles of eukaryotic cells arose from bacteria that came to live in a symbiotic relationship inside eukaryotic cells.

4

Endotoxin

A toxin incorporated into the outer layer of Gram-negative cells that is released when the cell dies.

5

Energy of activation

The energy needed to start a chemical reaction.

3

Enteric

Having to do with the intestine.

22

Enteric fever

A systemic infection with a focus on the intestinal tract.

22

Enterobacteriaceae

A family of bacteria, many of which are intestinal Gram-negative facultative anaerobes that have flagella.

22

Enterocytes

Epithelial cells of the large and small intestine.

22

Enterohemorrhagic E. coli

A type of Escherichia coli that causes destruction of the blood vessels; the causative agent in infections seen with contaminated ground beef.

22

Enterotoxin

An exotoxin that attacks the tissues of the intestinal tract.

5

Enveloped virus

A virus with a lipid bilayer surrounding its capsid.

12

Enzyme immunoassay

Analytical approach where an enzyme bound to an antigen or antibody is used to produce a signal for detection.

6

Enzyme–substrate complex

The association of the enzyme with its substrate.

3

Eosin methylene blue  (EMB)

A blue dye used for a variety of bacterial stains, both simple and differential.

10

Eosinophil

A white blood cell normally found in very low numbers in the blood but in very high numbers during a parasitic infection.

15

Eosinophilia

An abnormal increase of eosinophils in the blood.

14

Epidemic disease

A disease that has a higher than normal incidence in the population over a short period.

6

Epidemic typhus

A louse-borne rickettsial disease caused by Rickettsia prowazekii; seen most often in conditions of overcrowding and poor sanitation.

25

Epidemiology

The study of factors and mechanisms involved in the spread of disease within a population.

6

Epididymitis

Infection of the epididymis.

23

Episome

A DNA segment in bacterial cells that can exist as part of a chromosome, or separate from the chromosome.

25

Epithelial hyperplasia

An increase in epithelial cell number in response to a specific stimulus, such as infection with a pathogen.

14

Epitope

Area of an antigen molecule to which specific antibodies bind; also called an antigenic determinant.

16

Epstein–Barr virus

A virus that causes Burkitt’s lymphoma and mononucleosis.

25

Erysipelas

A rapidly spreading infection of the deeper layers of the dermis.

26

Erythema

Redness of the skin due to congestion of the capillaries.

25

Eschar

The thick crust or scab that forms, for example, over a severe burn.

26

Etiology

The cause of a disease.

7

Eukaryote

A cell that has a distinct nucleus and other membrane-enclosed organelles.

4

Exfoliatin

An exotoxin produced by Staphylococcus aureus and seen in scalded skin syndrome.

26

Exocytosis

Process in which vesicles inside a cell fuse with the plasma membrane and release their contents to the outside of the cell.

4

Exogenous infection

An infection caused by organisms that enter the body from the outside.

22

Exotoxin

A soluble protein toxin produced by living bacteria. It is seen in many types of systemic infection.

5

Extravascular infection

An infection outside of the bloodstream.

25

Extreme halophile

A bacterium that thrives in extremely high concentrations of salt.

10

Extreme thermophile

A bacterium that grows at temperatures above 80°C.

10

Exudate

Fluid containing high levels of protein and cellular debris that is deposited in tissues or on tissue surfaces.  It is usually the result of inflammation.

21

F1 protein

A factor seen in plague that forms a gel-like capsule preventing phagocytosis and allowing the bacteria to multiply in the submucosa.

25

Facilitated diffusion

Diffusion across a membrane that is carried out by a nonspecific carrier molecule and does not require ATP.

9

Factors B, D, and P (properdin)

Chemical molecules found in the blood that can bind to antigens on the surface of microbes and initiate the alternative complement pathway.

15

Facultative anaerobe

A bacterium that uses oxygen for metabolism but shifts to anaerobic metabolism when oxygen is no longer available.

3

Facultative halophile

A bacterium that can grow in high concentrations of salt as well as normal concentrations of salt.

10

FAD (flavin adenine dinucleotide)

A coenzyme that carries hydrogen atoms and electrons.

3

Fasciitis

Infection of the fascia of the body.

26

Fastidious bacteria

Bacteria that do not grow well without specific supplements added to the medium. Even then, these bacteria can take longer to grow than other organisms.

10

Fatal familial insomnia

A very rare prion disease of the brain causing complete sleeplessness.  It is untreatable and fatal.

8

Fatty acid

A long chain of carbon and hydrogen atoms with a carboxyl group at one end.

2

Favus

A disease causing hair loss due to permanent destruction of the hair follicle, resulting in bald spots associated with crusty scarred skin.

14

Fecal coliform

A Gram-negative, rod-shaped, facultatively anaerobic bacterium associated with fecal contamination.

10

Fecal coliform count

A test done to determine the level of fecal coliform contamination in water.

10

Fecal–oral route of contamination

A major route of infection associated with poor sanitation and hygiene.

5

Feedback inhibition

A regulatory mechanism in which a product in a reaction inactivates an enzyme necessary for the reaction to proceed.

3

Fever

A body temperature that is abnormally high.

15

Filariasis

Disease of the blood and lymph caused by any of several different roundworms.

25

Fimbria (plural fimbriae)

Also known as an attachment pilus. A short hairlike appendage found exterior to the cell wall. It is used as a mechanism for staying in the host during infection.

5

Flagella (singular flagellum)

Long thin helical appendages found on certain cells. They provide a means of locomotion.

9

Flagella stain

A technique used for observing flagella by coating the surface of the flagella with multiple layers of dye or metal such as silver.

4

Flagellates

Parasitic protozoan organisms that use flagella to move.

14

Flagellin protein

Globular protein that forms the flagella.

9

Flucytosine

An antifungal antibiotic used in the treatment of severe candidal and cryptococcal infections.

19

Fluid mosaic model of the membrane

Model incorporating all of the structures found in the cell membrane and based on the phospholipid bilayer structure of the plasma membrane.

4

Flukes

Adult trematodes that can live for decades in human tissue and blood vessels.

14

Fluorescent molecules

Molecules that emit light after absorbing light of a different wavelength.

6

Fluorescent proteins

Proteins that emit light after absorbing light of a different wavelength.

6

Flushing

Transient redness of the face and neck.

8

Focus of infection

An area where the infection is localized and from which it can spread to other parts of the body.

7

Follicles

Areas of the lymph node where B cells are found.

16

Folliculitis

Inflammation of the follicles.

14

Fomites

Nonliving substances (such as clothing, dishes, or paper money) that are capable of transmitting disease.

6

Forespore

The structure formed during the development of a spore in which the plasma membrane wraps around the developing spore.

9

Formalin

A 37% solution of formaldehyde used in clinical settings for disinfection.

18

Fosfomycin

Antibiotic that targets the murA gene and prevents peptidoglycan subunits from being produced.

9

Frameshift mutation

Mutation resulting from an insertion or deletion of one or more bases in DNA.

11

Freeze-drying

Also referred to as lyophilization. It is a method of extracting water from a frozen state.

18

GALT (gut-associated lymphoid tissue)

A collective name for tissues of lymphoid nodules, especially those in the digestive tract.

16

Gametocyte

A male or female sex cell.

14

Gametogony

The development of merozoites into male and female gametes, that later fuse to form a zygote.

14

Gamma hemolysis

A type of hemolysis in which there is no destruction of red blood cells.

10

Ganciclovir

A derivative of acyclovir used to treat retinitis caused by cytomegalovirus infection.

19

Gas gangrene

A deep wound infection in which tissue is destroyed, often caused by species of the genus Clostridium.

5

GasPak™ jar

A container used to incubate obligate anaerobic organisms.

10

Gastritis

Inflammation of the stomach.

22

Gene constellations

The term used to describe clusters of genes that determine virulence.

8

Gene expression

The process of transcription and translation.

11

Generalized transduction

Type of transduction in which a fragment of DNA from the degraded chromosome of an infected bacterial cell is accidentally incorporated into a new bacterial virus particle, which can then be transferred to another cell.

11

Generation time

The time required for a population of organisms to double in number.

10

Genetic code

The one-to-one relationship between each codon and a specific amino acid.

11

Genetic engineering

Process of changing the genetic information of an organism.

6

Genital herpes

Primarily sexually transmitted disease of the genital region which can give rise to confluent ulcerations.

13

Genomics

Discipline in genetics considering entire genomes rather than individual genes.

6

Genotyping

Determination of the genotype of an organism in comparison to a reference organism.

6

Genus

A taxonomic term consisting of one or more species.

4

Germ theory of disease

The theory that diseases can be caused by microorganisms.

1

German measles

Also known as rubella. A viral infection characterized by a short-term skin rash.

26

Germination

The mechanism by which organisms develop from the endospore state to the vegetative (growing) state.

9

Gerstmann–Sträussler–Schenker syndrome

A group of rare prion diseases having the common characteristic of cognitive and motor disturbances.

8

Ghon complex

Calcified necroses seen in the tubercles, associated with tuberculosis.

21

Giardiasis

A gastrointestinal disorder caused by the flagellated protozoan Giardia.

14

Gingiva

The soft tissue (gums) in the mouth.

22

Gingivitis

The mildest form of periodontal disease characterized by inflammation of the gingiva.

22

Glycocalyx

A term used to refer to all substances containing polysaccharides that are found external to the cell wall.

9

Glycolipid

A lipid molecule that contains carbohydrate.

2

Glycolysis

An anaerobic metabolic pathway used to break down glucose into pyruvate; it produces some ATP.

3

Golgi apparatus

An organelle found in eukaryotic cells that receives, modifies, and transports substances coming from the endoplasmic reticulum.

4

Gonorrhea

A sexually transmitted infection caused by Neisseria gonorrhoaea, commonly asymptomatic in females but marked by a painful purulent discharge from the urethra in males.

4

gp41

A protein found on HIV.

17

gp120

A protein found on HIV.

17

Gram stain

A differential stain that differentiates bacteria into either Gram-positive or Gram-negative groups.

4

Granulocyte

A leukocyte (white blood cell) with granular cytoplasm and an irregularly shaped nucleus.

15

Granulocyte–macrophage colony-stimulating factor (GM-CSF)

A substance that recruits large numbers of phagocytic cells to the site of infection.

15

Granuloma

A collection of epithelial cells, macrophages, lymphocytes, and fibers seen in chronic inflammation.

7

Granulysin

A peptide secreted by killer cells that causes the onset of apoptosis.

16

Granzyme

A protease enzyme secreted by killer cells that causes the death of a target cell by triggering apoptosis.

15

Graves’ disease

Autoimmune disease in which antibodies attack thyroid stimulating hormone causing it to be overproduced, leading to hyperthyroidism.

17

Group translocation

One of three types of active transport seen in bacteria, in which chemical substances brought into the cell are chemically modified so they cannot diffuse back out of the cell.

9

Gruber reaction

Identifying an unknown antigen by using a known antibody.

6

Gummas

Localized granulomatous lesions seen in the skin, bones, joints, and internal organs in tertiary syphilis.

23

H antigen

Refers to the proteins that make up the flagella of bacteria; they are antigenic and can initiate an immune response.

22

Hairy Leukoplakia

White patch on the tongue or buccal mucosa caused by Epstein–Barr viral infection and associated with HIV infection.

17

Halophile

A salt-loving organism that requires a moderate to extreme level of salt so as to grow. There are three categories: obligate, facultative, and extreme.

10

Hard measles

Common form of measles; also called rubeola.

26

Hashimoto’s thyroiditis

Autoimmune disease causing the destruction of thyroid tissue.

17

Heavy chain of the antibody molecule

Two of the four polypeptide chains that make up the antibody molecule. The heavy chains have a greater molecular weight than the other two chains which are called the light chains.

16

Helical symmetry

Also known as symmetry.  The “spiral staircase” arrangement of the DNA molecule, which has a precise symmetry.

12

Helicase

An enzyme that unwinds the helical structure of the DNA during replication.

11

Helminth

A worm with bilateral symmetry; includes roundworms and flatworms.

14

Helper T cell

The T lymphocyte that stimulates the function of other immune cells such as B cells, cytotoxic T cells, and macrophages.

16

Hemagglutinin

A glycoprotein on the envelope of some viruses, which assists in attachment to and entering the host cell.

12

Hematogenous dissemination

Movement through the blood; the most efficient way for systemic viruses to disseminate throughout the body.

13

Hemolysin

An enzyme that destroys red blood cells.

5

Hemoptysis

The spitting of blood or bloodstained sputum.

21

Hemorrhagic colitis

Infection of the colon with bloody discharge.

22

HEPA filter

A high-efficiency particulate air filter containing holes that are too small for microorganisms to pass through. It is used to keep rooms sterile.

18

Hepatitis

An inflammation of the liver usually caused by viral infection but can also be caused by an ameba or by toxic chemical damage to the liver.

7

Hepatocellular carcinoma

Malignancy involving cells of the liver.

22

Hepatomegaly

Enlargement of the liver.

21

Hepatosplenomegaly

Enlargement of both the liver and the spleen.

25

Herd immunity

The proportion of individuals in a population who are immune to a particular disease.

6

Hermaphrodites

Term used to describe the reproductive system of some flukes that have both male and female reproductive systems.

14

Heterotrophy

The use of carbon atoms from preexisting organic molecules to produce new biomolecules.

3

Hfr (high frequency of recombination) cell

An F bacterial cell that harbors a F plasmid incorporated in its chromosome.

11

Highly virulent

The condition in which a microbe is extremely harmful and damaging to the host.

4

Histamine

A chemical that is produced and stored by mast cells and basophils that can cause vasodilation in the inflammatory response.

15

Histatins

Antimicrobial proteins found in saliva that also enhance the migration of epithelial cells and fibroblasts to speed up wound healing.

15

Histoplasmosis

A fungal respiratory disease endemic to the central and eastern United States, caused by Histoplasma capsulatum.

14

Homolactic fermentation

Fermentation in which pyruvate is converted into lactate.

3

Hong Kong influenza

One of the three major influenza epidemics in the United States. It occurred in 1968 and caused more than 30,000 deaths.

8

Horizontal gene transfer (HGT)

The transfer of genetic material between organisms not involving a reproductive cellular division.

20

Human papillomavirus (HPV)

Virus that attacks skin and mucous membranes, causing papillomas or warts. It has been proved to cause cervical carcinoma.

23

Humoral immunity

A response to infection involving the production of antibodies.

16

Hybridization

The binding of oligonucleotides to a complementary sequence of nucleotides.

6

Hydrogen bond

A relatively weak bond between a hydrogen carrying a partial positive charge and an oxygen or nitrogen molecule carrying a partial negative charge.

2

Hydrolysis

A chemical reaction that produces smaller products by using water to break down larger molecules.

2

Hydrophilic

Having an affinity for water.

2

Hydrophobic

Lacking an affinity for water.

2

Hygiene hypothesis

The theory that a less hygienic environment can help protect against certain allergens.

17

Hypersensitivity

Also called allergy. It is a disorder in which the immune system reacts to antigens that it would normally ignore.

17

Hypertonic

A solution containing a concentration of dissolved material greater than that within a cell.

9

Hyphae

Long threadlike extensions of the cytoplasm seen in molds.

14

Hypotonic

A solution containing a concentration of dissolved materials lower than that within the cell.

9

Hypoxia

Condition resulting from reduced levels of oxygen being supplied to the tissues.

21

Iatrogenic

Transmission of infection because of poor techniques employed by health care workers.

13

ICAM-1

A cell receptor used for rhinovirus infection.

12

Icosahedral symmetry

Also known as symmetry. Capsid arrangement seen in some viruses in which there are 20 geometric sides that make up the virus protein coat.

12

ID50

Infectious dose 50%. The number of organisms required to infect 50% of the subject population.

5

Immune escape

Refers to the ability of some pathogens to evade the host immune response.

9

Immunocompromised

Refers to an individual whose immune defenses are weakened. It can result from a variety of causes such as HIV infection, drug therapy for malignancy or transplantation as well as old age or debilitation.

1

Immunofluorescence

Analytical approach where fluorescent molecules are bound to an antigen or antibody to produce a signal for detection.

6

Immunoglobulin

Also known as an antibody. A class of proteins that are produced by the humoral immune response and respond to a specific antigen.

16

Immunological memory

The ability of the adaptive immune response to immediately recognize and respond against antigens it has previously been exposed to.

16

Impetigo

A highly contagious pyoderma caused by staphylococci or streptococci, or both.

26

Inactive vaccine

Also known as a killed vaccine. A vaccine composed of virus that is either dead or inactivated.

13

Incidence of disease

The number of new cases of a particular disease seen in a population over a specific period of time.

6

Inclusion bodies

(1) Form of cytopathic effect in which viral particles, viral components, or remnants of virus aggregate in the cytoplasm of infected cells. (2) The aggregation of reticulate bodies seen in Chlamydia. (3) In bacteria, used for storage of materials.

5

Incubation period

The time between exposure to the pathogen and the first appearance of signs and symptoms of the infection.

7

Index case

The first person to have been infected with the disease.

6

Indirect method

A measurement of bacterial growth in which cells or colonies are estimated, not observed.

10

Infectious endocarditis

Infection of the heart.

24

Inflammation

The body’s defensive response to any trauma or infection of the body.

15

Influenza

An acute viral infection of the respiratory tract marked by inflammation of the nasal mucosa, pharynx, and conjunctiva.

1

Inhalation anthrax

One of several types of anthrax infection caused by Bacillus anthracis, resulting in highly fatal pneumonia.

1

Initiation codon

The sequence of messenger RNA that sets the reading frame.

11

Initiator protein

The protein that recognizes the replicator sequence and begins transcription.

11

Innate immune response

The nonspecific immune response that is present at birth.

1

Inoculate

To add microorganisms to growth medium to start a culture.

6

Integral protein

Membrane protein that extends through the entire membrane.

9

Interferon

A group of small protein molecules often released in response to a viral infection that bind to noninfected cells, causing them to produce antiviral proteins that protect against viral infection of the cell.

15

Interleukin 1 (IL-1)

The best-known endogenous pyrogen, which causes the onset of fever during an infection.

15

Interleukin 6 (IL-6)

A cytokine produced during an infection that causes the liver to produce acute-phase proteins.

15

Interleukins

A class of cytokine produced by leukocytes.

15

Intermediate host

An organism in which a parasite develops but does not undergo sexual reproduction.

14

Interstitial macrophages

Cells found in the stroma of the lung. They are smaller and less phagocytic than alveolar macrophages.

15

Intravascular infection

An infection within the bloodstream.

25

Invasin

A virulence factor.

5

Iodophor

An organic compound that incorporates iodine in such a way that the iodine is released slowly.

18

Ionic bond

The bond that forms between cations and anions due to their opposing charges.

2

Ionizing radiation

Form of radiation that causes disruption of the electron clouds surrounding atoms, causing the ionization of the atoms.

18

Ions

Electrically charged atoms produced when atoms either gain or lose electrons.

2

Isoelectric focusing

Technique to separate molecules by means of differences in their isoelectric point.

6

Isotonic

Fluid containing the same concentration of dissolved materials as that inside the cell.

9

Isotype

A term referring to one of the five types of constant regions of antibodies.

16

J chain

The protein found on the pentameric form of IgM and the dimeric form of IgA that helps to hold the monomers together.

16

Jaundice

Yellowness of the skin, sclera, mucous membranes, and excretions caused by hyperbilirubinemia.

14

K antigen

Refers to the polysaccharide associated with the capsule found around certain bacteria.

22

Kaposi’s sarcoma

A malignancy associated with immunodeficiency in which blood vessels grow in tangled masses that are filled with blood and easily ruptured.

17

Keratitis

Infection of the cornea of the eye.

26

Killed vaccine

Also known as an inactive vaccine. A vaccine composed of virus that is either dead or inactivated.

13

Kinin

A protein that causes vasodilation and attracts phagocytic cells to the site of injury in the process of inflammation.

15

Koch's postulates

Four postulates proposed by Robert Koch in the nineteenth century, used to prove that a particular organism causes a particular disease.

7

Koplik’s spots

Red spots with centralized bluish specks that appear on the mucous membranes in the early stages of measles.

26

Kupffer cell

A phagocytic cell that is stationed in the sinusoids of the liver.

15

Kuru

Transmissible spongiform encephalopathy of the human brain. The disease is caused by prions and is associated with cannibalism and with tissue or organ transplantation.

8

Lac operon

A sequence of genes that controls the production of enzymes required to break down the sugar lactose.

11

Lacrimal apparatus

The structures associated with the production and recycling of tears.

15

Lacrimal gland

The gland that produces tears. It is part of the lacrimal apparatus.

15

Lag phase of bacterial growth

The first phase of the bacterial growth curve, in which organisms acclimate to their surrounding; they grow in size but do not increase in number.

10

Lagging strand

Also known as the discontinuous strand. The strand of DNA that is replicated in pieces called Okazaki fragments.

11

LAL assay

The Limulus amebocyte lysate assay, which is used to determine whether there is endotoxin contamination.

5

Langerhans cells

Dendritic cells found in the layers of the skin. They are phagocytes that are one type of antigen-presenting cell.

15

Lantibiotics

Antibacterial peptides produced by some Gram-positive bacteria.

20

Laryngotracheitis

Also known as acute croup. A severe infection of the larynx and trachea.

21

Latency (latent)

Pertaining to a virus that has entered a host cell and its nucleic acids have been incorporated into the host's, but no new viruses are produced.

12

Latent infection

A disease in which there are periods of inactivity either before the onset of symptoms or between attacks.

13

Latent syphilis

A stage of syphilis in which there are no symptoms or signs of infection.

23

LD50

Lethal dose 50%. The number of organisms required to kill 50% of the subject population.

5

Leading strand

Also known as the continuous strand. The strand of DNA that is replicated continuously.

11

Lectin-binding pathway

The complement pathway that is activated by the carbohydrate mannose.

15

Leishmaniasis

Infection with the parasite Leishmania.

14

Leprosy

A chronic disease caused by Mycobacterium leprae which is characterized by granulomatous lesions of the skin, mucous membranes, and central nervous system.

7

Leukocidin

An exotoxin produced by many bacteria that kills white blood cells, including phagocytic cells.

5

Leukocyte

A white blood cell.

15

Leukocyte endogenous mediator

A factor that lowers plasma iron concentration, which limits the availability of iron and thereby inhibits the growth of some pathogens.

15

Leukotriene

A chemical substance released from mast cells that causes prolonged airway constriction, increased dilation and permeability of capillaries, increased secretion of mucus, and stimulation of nerve endings that causes pain and itching.

15

Light chain of the antibody molecule

Two of the four polypeptide chains that make up the antibody molecule. The light chains have a lower molecular weight than the other two chains which are called the heavy chains.

16

Lipid A

A component of the lipopolysaccharide layer of Gram-negative cells, which becomes an endotoxin upon release from the cell.

9

Lipid carrier cycle

In cell wall synthesis, the transport of peptidoglycan precursors (NAG and NAM) through the cell membrane by lipids.

9

Lipid raft

A portion of the plasma membrane of host cells that contain an increased portion of lipid.

12

Lipocalin

A substance that inhibits the scavenging of iron by pathogens, thereby inhibiting their growth.

15

Lipopolysaccharide layer

An outer layer of the cell wall found around Gram-negative cells. It contains endotoxin that is released when the organism dies and this layer falls apart.

9

Lipoteichoic acid

A molecule that is found only in Gram-positive bacteria that penetrates the entire cell wall and attaches to the plasma membrane of the cell.

9

Live attenuated vaccine

Live virus that has been weakened to reduce infectivity, used for some forms of vaccination.

13

Loaiasis

A disease caused by the parasitic Loa loa worm and transmitted to humans by the deer fly.

26

Local infection

An infection confined to a specific area of the body.

7

Lockjaw

The early symptom of tetanus, an infection of the nervous system that initially affects the small muscles of the face, preventing them from relaxing.

5

Log (exponential) phase of bacterial growth

The second of the four phases of bacterial growth, in which cells divide at an exponential rate.

10

Logarithmic decline phase

Also known as the death phase.  The fourth phase of bacterial growth, in which bacteria die faster than they divide.

10

Lophotrichous flagella

The arrangement in which there are two or more flagella at one or both ends of a bacterial cell.

9

Lymphadenitis

Inflammation of one or more lymph nodes.

23

Lymphangitis

Inflammation or infection of the lymphatic system.

25

Lymphocyte

A form of white blood cell that is involved with the adaptive immune response of the body.

15

Lymphogranuloma venereum

Venereal infection caused by Chlamydia trachomatis marked by a primary transient ulcerative lesion in the genital region.

23

Lymphoma

Any neoplastic disorder of the lymphoid tissues.

13

Lymphopenia

A reduced number of lymphocytes resulting from certain forms of infection and also from some kinds of therapy for malignancy or transplantation.

8

Lyophilization

Also referred to as freeze-drying. It is a method of extracting water from a frozen state.

18

Lysis

The bursting of a cell.

12

Lysosome

A small membrane-enclosed organelle seen in eukaryotic cells that contains digestive enzymes.

4

Lysozyme

An antibacterial enzyme found in secretions such as tears and saliva.

15

Lytic infection cycle

Pertaining to a virus, in which the host cell is infected by the virus, produces new viruses, bursts, and releases newly produced virions.

12

M cells

Specialized cells found in the digestive tract. They are used by pathogens to enter the tissues of the body.

15

M protein

A chemical virulence factor found on the bacterial cell surface and also on fimbriae that helps pathogens stay in the host.

5

Macrophage

A highly phagocytic white blood cell.

15

Macrophage activation

A process in which macrophages are stimulated by T_H1 helper cells to eliminate pathogens that proliferate in macrophages.

16

Macule

A discolored spot on the skin that is not raised above the surface.

26

Maculopapular rash

Broad lesions that slope away from a centrally located papule.

25

Major histocompatability complex (MHC) 

A group of cell surface proteins that are required for the development of an immune response.

16

Malaise

A vague feeling of discomfort.

8

Malarial paroxysm

The term used to describe the acute phase of infection seen in malaria.

14

MALT

Mucosa-associated lymphoid tissue.

16

Mannose-binding protein (MBP)

Acute-phase protein that binds to mannose sugars found on many bacterial and fungal cell membranes.

15

Margination

The process in which white blood cells traveling in the blood are able to slow down and stop adjacent to the area where the tissue injury has occurred. It is caused by the localized secretion of selectin, which is a sticky molecule on the inner side of the vessels.

15

Mass spectrometry

Analytical technique used to identify amount and type of molecules in a sample via measuring the mass-to-charge ratio and abundance of ions in a gas phase.

6

Mast cell

A white blood cell that releases histamines during an allergic response.

15

Matrix protein

The second layer of viral protein found just inside the envelope of the virus.

12

Mature vegetation  

A “mesh” of platelets, fibrin, and inflammatory cells seen in infectious endocarditis.

25

Maximum growth temperature

The highest temperature at which an organism will grow.

10

Measles

Also known as rubeola. A highly contagious viral infection usually seen in children. It involves the respiratory tract and is marked by discrete red papules, which become confluent.

5

Mechanical vector transmission

The passive movement of organisms from a vector to a human or fomite.

6

Membrane attack complex (MAC)

The complex formed during the final stages of the complement pathway. This complex produces a hole in the cell wall of bacteria, leading to their death.

15

Memory cell

A long-lived T or B lymphocyte that is derived as part of the adaptive immune response. It retains a memory of the antigen that it was sensitized to.

16

Meninges

Connective tissue layers that cover the brain and spinal cord.

24

Meningitis

Infection of the meninges (layers) that surround the brain and spinal cord.

8

Meningoencephalitis

Inflammation of the brain and meninges.

24

Merozoite

A trophozoite form of the malaria parasite derived from sporozoites. It is found in red blood cells and hepatocytes during the malaria infection cycle.

14

Mesophiles

Organisms that grow best at temperatures between 25°C and 40°C.

10

Messenger RNA (mRNA)

A type of RNA that results from the transcription of DNA and carries information about the arrangement of amino acids in a protein.

11

Metabolism

The sum of catabolism (the breakdown of organic molecules) and anabolism (the building up of organic molecules).

3

Metacercariae

Encysted form of cercariae seen in the development of a fluke.

14

Metachromatic granules

Polyphosphate granules seen in the cytoplasm of certain bacteria.

9

Metagenome

Term used to refer to genomes from a mixed community of organisms.

7

MHC restriction

Major histocompatability complex restriction associated with the interaction of antigen-processing cells and helper T cells.

16

Microaerophilic bacteria

Organisms that grow best in the presence of small amounts of oxygen.

10

Microarray analysis

A type of biological analysis method that is used in a variety of biotechnology processes.

6

Microbial antagonism

The ability of normal microbial flora to inhibit the growth of pathogens by competing for resources.

7

Microbial flora

Microorganisms that are normally found living in and providing important benefits to the host.

7

Microbiota

Microbial population within a habitat.

7

Microfilament

A protein fiber that makes up part of the cytoskeleton in eukaryotic cells.

4

Microfilariae

Live offspring of tissue nematodes that circulate in the blood and subcutaneous tissues until they are ingested by specific blood-sucking insects.

25

Microglial cells

Resident macrophages found in the central nervous system. There are two forms, ameboid (which travel through developing brain tissue and are also found in damaged brain tissue) and ramified (found in normal brain tissue).

15

Microtubule

A protein tubule that forms the structure of cilia, flagella, and part of the cytoskeleton in eukaryotic cells.

4

Minimal bactericidal concentration

The lowest concentration of an antibacterial agent required to kill a bacterium.

20

Minimal inhibitory concentration (MIC)

The lowest concentration of an antimicrobial agent that prevents growth in the dilution method of determining antibiotic sensitivity.

18

Minimum growth temperature

The lowest temperature at which an organism will grow.

10

Miracidia

The ciliated free-swimming first-stage fluke larvae that have emerged from eggs.

14

Mitochondria (singular mitochondrion)

A membrane-enclosed organelle found in eukaryotic cells that is responsible for the production of ATP.

4

Moist heat

Hot air with a high moisture content. For example, steam.

18

Mold

The filamentous multicellular form of fungi.

14

Monocyte

A nonphagocytic white blood cell found in the blood that will differentiate into a phagocytic macrophage in response to an infection.

15

Mononuclear phagocytic system

Formerly called the reticuloendothelial system. It is a collection of phagocytic cells and tissues that contain phagocytic cells, located throughout the body.

15

Monotrichous flagellum

One of the four types of flagellar arrangement in which there is one flagellum seen on the cell.

9

Morbidity rate

The number of individuals affected by a disease during a set period divided by the total population.

6

Mordant

A substance used during staining that helps a dye bind to the cell.

4

Mortality rate

The number of deaths caused by a disease during a set period divided by the total population.

6

Motile structures

Cellular features used for movement (pseudopods, cilia, and flagella in protozoans).

14

MRSA

Methicillin-resistant Staphylococcus aureus.

1

Mucociliary escalator

Mechanism involving ciliated cells that allows materials in the bronchi, trapped in mucus, to be lifted up into the pharynx and subsequently swallowed or spat out.

15

Mucocutaneous candidiasis

A fungal infection of the mucosal tissues caused by the fungus Candida albicans.

14

Mucopurulent vaginal discharge

Vaginal discharge containing mucus and pus.

23

Multiple sclerosis

Neurological disease in which autoimmunity causes production of antibody against antigens on the myelin sheath of neurons.

17

Mumps

An acute contagious disease usually seen in children. It is caused by a paramyxovirus and chiefly affects the parotid salivary glands.

4

Mupirocin

An antibiotic that prevents colonization of the nasal passages with S. aureus.

9

Murein

Also known as peptidoglycan, a bacterial cell wall component.

9

Mutagen

An agent that causes mutations in DNA.

11

Mutualism (mutualistic)

A form of symbiosis in which two organisms of different species live in a relationship in which both benefit.

4

Myalgia

Muscular pain.

8

Myasthenia gravis

Genetic disorder of infants characterized by apnea, weakness, and fatigue.

17

Mycelium

A mass of long threadlike intertwining structures called hyphae.

14

Mycolic acid

A waxy substance found in the cell wall of certain bacteria, such as the genus Mycobacterium.

5

Mycosis (plural mycoses)

A disease caused by fungi.

14

Myocarditis

Inflammation of the muscular walls of the heart.

8

N-acetylglucosamine (NAG)

One of the repeating disaccharides that make up the cell wall of bacteria.

9

N-acetylmuramic acid (NAM)

One of the repeating disaccharides that make up the cell wall of bacteria.

9

NAD (nicotinamide adenine dinucleotide)

A coenzyme that carries hydrogen atoms and electrons.

3

Naive lymphocyte

A lymphocyte that has not found the antigen that binds to its receptor.

16

Nanocantilever

A beam that is immobilized at one end and the other end is free.

6

Nanotechnology

Technologies operating at the nanoscale.

6

Narrow spectrum antibiotics

The range of activity of an antimicrobial agent that attacks only a few kinds of microorganism.

19

Nationally notifiable disease

A disease that must be reported to the Centers for Disease Control and Prevention (CDC).

6

Natural killer cells (NK cells)

Large granular cells found in the peripheral tissue and blood that kill tumor cells, virus-infected cells, bacteria, fungi, and parasites.

15

Necrotizing fasciitis

An infection in which the fascia is destroyed by organisms such as group A streptococci either alone or in a synergistic way with other bacteria.

5

Necrotizing periodontal disease (NPD)

Also known as Vincent’s disease or trench mouth. A spectrum of acute inflammatory diseases resulting in the destruction of the soft tissue of the oral cavity.

22

Negri body

A characteristic cytopathology seen in rabies virus infections. These are areas in the cytoplasm that contain masses of viral particles.

5

Nematode

Roundworm.

14

Neonatal gonorrheal ophthalmia

Infection of the eyes of newborn babies from women with gonorrhea. It is caused by infection as the newborn travels down the birth canal.

26

Nephritis

Inflammation of the kidneys.

23

Neuraminidase

A glycoprotein on the envelope of some viruses, which assists in release from the host cell.

12

Neurotoxin

A toxin that acts on the tissues of the nervous system.

5

Neutropenia

A lower than normal number of neutrophil white blood cells.

6

Neutrophil

A phagocytic white blood cell.

15

Non-cytocidal effect

Viral cytopathology that causes a shutdown of host cell function.

5

Non-gonococcal urethritis

The most prevalent sexually transmitted disease.  Caused by Chlamydia trachomatis.

23

Non-ionizing radiation

A type of radiation, such as ultraviolet radiation, that causes the formation of thymine dimers in DNA.

18

Nonpolar covalent bond

The equal sharing of electrons between two atoms.

2

Nonseptate fungus

A fungus in which the hyphae do not have septa.

14

Northern Blot

Analytical tool to detect RNA in a sample.

6

Nosocomial infection

An infection that occurs during a hospital stay.

1

Nuclear membrane

Also called the nuclear envelope. It is the membrane surrounding the nucleus seen in eukaryotic cells.

4

Nuclear region of bacterial cell

Also called a nucleoid. It is the central location where DNA, RNA, and some proteins are found in bacterial cells.

9

Nucleocapsid

The area of the virus in which the capsid and the nucleic acid are found.

12

Nucleoli (singular nucleolus)

Areas in the nucleus of eukaryotic cells where ribosomal RNA is made and ribosomal assembly takes place.

4

Nucleoplasm

The semifluid portion of the cell nucleus of eukaryotic cells that is surrounded by the nuclear membrane.

4

Nucleoproteins

Viral proteins attached to the inner side of the capsid that holds viral nucleic acid in place.

12

Nucleotide excision

The repair mechanism in which enzymes look for distortions in the helical structure of DNA and excise those regions.

11

Nutrient agar

A formulation of media solidified by agar, used for the growth of many types of bacteria.

10

Nutrient broth

A formulation of media in fluid form, used for the growth of many types of bacteria.

10

Nutrient medium

A complex bacterial growth medium in which proteins provide energy, carbon, nitrogen, and other essential nutrients.

10

O antigen

Lipopolysaccharide found on the outer layer of Gram-negative bacteria.

22

O polysaccharide

A type of polysaccharide found on the cell wall of bacteria.

9

Obligate aerobe

A microorganism that cannot grow without oxygen.

10

Obligate anaerobe

A microorganism that cannot grow in the presence of oxygen.

10

Obligate halophile

A microorganism that requires higher than normal concentrations of salt for its growth.

10

Obligate intracellular parasite

The definition of a microorganism that requires entry into a host cell to reproduce.

5

Oculoglandular tularemia

Purulent conjunctivitis caused by Francisella tularensis.

25

Okazaki fragments

Pieces of DNA that are made on the lagging strand of DNA during replication.

11

Oligonucleotide probe

Short sequence of nucleotides that match a specific region of nucleic acid. 

6

Oncogenic virus

A virus that causes the host cell to become cancerous.

13

Oncovirus

Also known as an oncogenic virus. A virus that causes the host cell to become cancerous.

13

Oocyst

The encysted or encapsulated stage in the development of any sporozoan.

14

Open reading frame

The starting point for protein synthesis on messenger RNA.

11

Operator site on DNA

A gene in an operon that can bind repressor proteins and inhibit the transcription of the structural genes of the operon.

11

Operon

A sequence of genes that includes both structural and regulatory genes controlling transcription.

11

Opisthotonos

The last stages of tetanus in which the body bends backwards as a result of the relentless contraction of the muscles without relaxation.

24

Opportunistic infection

Infection caused by a microorganism if the immune status of the host is low.

6

Opportunistic pathogen

Resident or transient microorganisms that do not ordinarily cause disease but can do so under certain circumstances.

4

Opsonin

Any molecule that when bound to a microbe enhances the phagocytosis of that microbe by a phagocytic host cell.

15

Opsonization

The process by which microorganisms are rendered more attractive to phagocytes by being coated with antibodies (opsonins) and/or C3b complement proteins.

5

Optimal growth temperature

The temperature at which microorganisms grow best.

10

Organelle

A structure found in the cytoplasm of eukaryotic cells.

4

Origin of replication

The point on the DNA where replication begins.

11

Osmosis

A special type of diffusion in which water “chases” (moves toward) a higher concentration across the plasma membrane.

9

Oxidation

A chemical reaction in which a substance loses one or more electrons.

3

P pilus

A structure that projects from the exterior of a bacterial cell wall and binds to receptors on the epithelial cells of the urinary tract.

23

P site

The area of the ribosome that holds the growing chain of amino acids.

11

Pancreatitis

Inflammation of the pancreas.

8

Pandemic

Global proportions of an epidemic.

6

Papillomavirus

A virus that can cause warts; it is associated with human cervical cancer.

23

Papule

Small elevated lesion of the skin.

25

Paracortical area of the lymph node

An area of the lymph node where T cells are found.

16

Paragonimiasis

Infection with the lung fluke Paragonimus.

14

Paranasal conidiobolomycosis

Infection of the submucosa of the paranasal sinuses, resulting in the formation of granulated fibrotic tissue filled with eosinophils.

14

Parasite-directed endocytosis

A unique process in which the microvilli of the epithelial cells surround the organism and escort it into the cell cytoplasm. This process is seen in gonorrhea infection.

23

Parasitemia

Parasites in the blood.

14

Parasitism

A symbiotic relationship in which one organism (the parasite) benefits at the expense of the host.

7

Parenteral route

A portal of entry in which the barrier of the skin is broken, as in a cut, puncture, or surgical procedure.

5

Passive agglutination

Type of agglutination with the antigen first bound to an inert particle to detect an antibody.

6

Passive immunization

A procedure in which an already formed immune product such as antibody is administered to a patient.

13

Passive transport

Movement of materials across the membrane without the expenditure of ATP.

9

Pasteurization

Mild heating to destroy pathogens and other organisms that cause spoilage.

18

Pathogen

An organism capable of causing disease.

4

Pathogen-associated molecular pattern (PAMP)

Molecules associated with groups of pathogens that can be recognized by the innate immune system.

15

Pathogenic

Causing damage in the host and thus disease.

1

Pathogenicity

The ability of a microorganism to cause damage in the host and thus disease.

1

Pathogenicity islands

Sections of the genome that include groups of genes coding for virulence factors that increase the pathogenicity of a microorganism.

4

PD50

Paralytic dose 50%. The number of organisms required to cause paralysis in 50% of a subject population.

13

Pediculosis

A form of lice infection.

26

Pellicle

(1) A thin protein film over the tooth that is the base for the development of a biofilm leading to plaque formation and tooth decay. (2) A strengthened plasma membrane seen in some protozoa.

5

Pelvic inflammatory disease (PID)

An infection of the pelvic cavity in females, caused by any of several organisms.

23

Penicillin

An antibiotic derived from a common blue mold that is used to kill specific bacterium in particular Gram-positive cocci.

19

Penicillin G

A naturally occurring form of penicillin that is taken by injection.

19

Penicillin V

A naturally occurring form of penicillin that is taken by mouth.

19

Penicillin-binding protein (PBP)

Proteins found in the cell walls of bacteria that function in the building of the wall structure. The β-lactam ring of penicillin binds to these proteins.

19

Pentamidine

An antibiotic used in the treatment of Pneumocystis infections, leishmaniasis, and African sleeping sickness.

19

Peptide bond

The bond that forms between amino acids in constructing the primary sequence of proteins.

2

Peptidoglycan

The major component of bacterial cell walls.

1

Peptidyl transferase reaction

The enzymatic reaction that links amino acids together by forming the peptide bond.

11

Perforin

An enzyme released by cytotoxic cells that leads to the destruction of target cells.

15

Period of convalescence

One of the five periods that characterizes disease, in which the patient is recuperating.

7

Period of decline

The fourth period used to characterize the disease process, in which the patient is getting better and symptoms are declining. This is the period when secondary infections can occur.

7

Period of illness

The third of the periods that are used to characterize disease, in which the symptoms are greatest. During this period the immune response is functioning at its maximum. This is also the period during which a patient may die.

7

Periodontitis

Inflammation of the gingiva of the oral cavity.

22

Peripheral tolerance

Immunological tolerance that is caused by the inactivation (anergy) in lymphocytes that encounter antigen without co-stimulatory signals.

16

Periplasmic space

The space between the cell membrane and the outer membrane in Gram-negative bacteria.

9

Peritrichous flagella

This is the arrangement in which flagella are distributed all over the cell.

9

Permease

An enzyme complex involved in the active transport of materials through the cell membrane.

9

Peroxidase

The enzyme used by bacteria to convert hydrogen peroxide to oxygen and water.

10

Peroxisome

Vesicles in eukaryotic cells that contain the enzymes peroxidase, catalase, and oxidase.

4

Pertussis

A highly contagious respiratory infection caused by Bordetella pertussis. Also known as whooping cough.

4

Petechiae

Pinpoint-sized hemorrhages most commonly found in skin folds. They are often seen in rickettsial diseases.

8

Petechial hemorrhaging

Capillary hemorrhage into the skin forming red or purple spots.

8

Peyer's patches

A collection of lymphoid nodules found at the junction between the small and large intestine.

7

Phage display

Technique used to study protein–protein or protein–DNA interactions that uses bacteriophages to display the protein partner.

6

Phage therapy

The use of bacteriophage to treat bacteria-infected hosts.

12

Phagetyping

Method for identifying strains of bacteria by means of bacteriophages that can infect them.

6

Phagocyte

A cell that can carry out phagocytosis.

5

Phagocytosis

Ingestion of materials into cells by means of vacuole formation.

5

Phagolysosome

A structure resulting from the fusion of a phagosome with a lysosome.

15

Phagosome

A vacuole that forms around an organism within the phagocyte that engulfed it.

15

Pharyngitis

Inflammation of the pharynx commonly called a sore throat.

21

Phase variation

A mechanism used by some microorganisms in which the number of pili decreases to prevent the binding of antibody.

9

Phenol

A powerful disinfectant compound used as the standard by which other disinfectants are measured.

18

Phenol coefficient

A numerical expression of the effectiveness of a disinfectant relative to that of phenol.

18

Phosphoenolpyruvate (PEP)

A high-energy molecule used by some bacteria for translocation.

9

Phospholipid

A lipid composed of glycerol, two fatty acids, and a polar head group. It is the basic unit seen in membrane structures.

2

Phosphorylation

The addition of a phosphate group to a molecule, often from ATP, which generally increases the molecule’s energy.

3

Photoautotroph

An autotroph that obtains energy from light.

3

Photoheterotroph

A heterotroph that obtains energy from light.

3

Photoreactivation

Also known as light repair. The process of using the enzyme photolyase to unlink thymine dimers in DNA.

11

Piedra

Colonization of the hair shaft by various species of fungi characterized by nodules affixed to the hair.

14

Pili (singular pilus)

Tiny hollow projections used to attach bacteria to surfaces (called attachment pili) or for the transfer of genetic material during conjugation.

9

Pilin protein

Globular proteins that make up the pilus structure.

9

Pinocytosis

The taking in of small molecules by invagination of the cell membrane.

4

Plasma cell

Activated B cells that produce antibodies.

16

Plasmid

An extrachromosomal piece of DNA that is small and circular and replicates independently. It can be transferred to another cell.

4

Plasmid fingerprinting

Method for identifying strains of bacteria by analyzing the plasmids they harbor.

6

Plasmolysis

The shrinking of a cell as a result of changes in the osmotic concentration resulting from loss of water in a hypertonic solution.

9

Pneumonia

Inflammation of the lungs.

1

Pneumonic plague

Also known as the Black Death. An infection of the lungs with Yersinia pestis, causing a highly contagious form of plague.

25

Pneumonitis

Inflammation of the lungs.

21

Point mutation

Also known as a missense mutation. A change in a single base of the DNA sequence.

11

Polycistronic

mRNA found in prokaryotes, encoding more than one protein.

11

Polymerase chain reaction (PCR)

Technology used to amplify DNA fragments.

6

Polyribosome

A long chain of ribosomes attached at different points along a strand of messenger RNA.

11

Porins

Proteins in the outer layer of Gram-negative bacteria that nonselectively transport polar molecules into the periplasmic space.

9

Portal of entry

A site at which microorganisms enter the body.

5

Portal of exit

A site at which microorganisms can leave the body.

5

Post-translational modification

Changing the structure of proteins so that antibodies do not recognize them.

9

Precipitation

Creation of an insoluble compound.

6

Prevalence

The number of people infected with a particular disease at any given time.

6

Primary amebic meningoencephalitis

Infection of tissues of the nervous system caused by parasites that have ameboid characteristics.

24

Primary cell line

A cell line that must be started from a tissue or organ before each use.

13

Primary immune response

The initial adaptive immune response to an antigen.

16

Primary immunodeficiency disease

A genetic or developmental defect in which T cells or B cells are lacking or nonfunctional.

17

Primary infection

An initial infection in a previously healthy individual.

7

Primary (obligate) pathogen

An organism that can cause disease in healthy hosts.

4

Primary syphilis

Early-stage syphilis infection, characterized by painless ulcerations on the genitals called chancres.

23

Primase

An enzyme that puts the RNA primer on the lagging strand of DNA during replication.

11

Primer:template junction

The area where the RNA primer is located on the strand of DNA. It is required for the replication of DNA.

11

Prion

An infectious protein.

8

Prion protein scrapie (PrPSC)

The abnormally folded, infectious, form of the prion protein.

8

Prodromal period of disease

The second phase of the disease process, in which nonspecific symptoms such as headache and malaise appear.

7

Prodrug

The inactive form of a drug that must be activated enzymatically once in the patient’s body.

19

Products

Substances created in a chemical reaction.

3

Proglottids

Reproductive segments seen in cestodes, which contain both male and female gonads.

14

Prokaryote

Microorganism that lacks a cell nucleus and membrane-enclosed organelles. All bacteria are prokaryotes.

4

Promoter site on DNA

The site where RNA polymerase binds to the DNA strand to begin transcription.

11

Propagated epidemic

Disease that involves people-to-people contact and stays in the population for a long time.

6

Properdin pathway

The alternative complement pathway that is activated by contact between lipopolysaccharides and endotoxins on the surface of pathogens and three factors found in the blood (factor B, factor D, and factor P).

15

Prophage

A sequence of DNA from a bacterial virus that is incorporated into the bacterial chromosome.

11

Prophylactic

A medicine or protocol used to prevent infection or disease.

19

Prospective analytical study

A type of epidemiology study in which analysis is ongoing while the disease is occurring.

6

Prostaglandins

Chemical mediators that act as cell regulators and are produced during the inflammatory response. They can stimulate pain and fever responses.

15

Prostatitis

Inflammation of the prostate gland.

23

Proteasome

Large proteins found in both prokaryotes and eukaryotes that degrade unneeded or damaged proteins.

4

Protein microarrays

Miniaturized assay systems that contain small amounts of proteins in a high-density pattern.

6

Proteomics

Discipline considering entire proteomes rather than individual proteins.

6

Proton motive force

A concentration gradient of protons seen during the chemiosmosis step during electron transport.

3

Protozoan

Single-celled, microscopic, animal-like organism.

4

Provirus

The combined nucleic acids of a virus and a host cell during latency.

12

PrPC protein

The normally folded form of the prion protein.

24

PrPSC protein

The abnormally folded, infectious, form of the prion protein.

24

Pseudopod

Bulge of cytoplasm used as a means of locomotion in some protozoa.

14

Psychrophiles

Bacteria that grow best at very cold temperatures, between 0°C and 15°C.

10

Psychotrophs

Bacteria that grow best at temperatures between 20°C and 30°C.

10

Purines

The nucleotide bases adenine and guanine.

11

Pustule

A small elevated pus-containing lesion of the skin.

26

Pyogenic bacteria

Pus-forming bacteria.

17

Pyrimidines

The nucleotides thymine and cytosine.

11

Pyrogens

Chemicals that can induce a fever response.

15

Pyruvate

A 3-carbon molecule created by glycolysis.

3

Pyuria

Pus in the urine.

23

Quaternary ammonium compound (QUATS)

Popular detergents containing ammonium cations. They are low-level disinfectants/antiseptics but are odorless, tasteless, and harmless to humans (except at high concentrations).

18

Quorum sensing

Type of decision-making process seen in bacteria that is based on the density of the population of bacteria.

4

Radiation

The energy that is emitted from atomic activities and dispersed at high velocity through matter or space.

18

Radioimmunoassay

Analytical approach where radioisotopes within an antigen or antibody are used to produce a signal for detection.

6

Radioisotope

Radioactive isotope of an element.

6

Reactants

Substances used up in a chemical reaction.

3

Reading frame

The mechanism used to read the DNA-coded sequence for transcription.

11

Real-time PCR

PCR where DNA amplification is measured via a fluorescence signal.

6

Re-assortment

Term used to describe changes in the DNA sequence.

8

Receptor-mediated endocytosis

The process of uptake of materials into the cell through binding to specific receptors on the cell membrane.

4

Recombinant DNA

Genetic material combined from multiple sources by means of genetic engineering.

6

Recombinant plasmid

Plasmid including DNA from two or more sources.

6

Recombination

The combining of DNA from two different cells, resulting in a recombinant DNA molecule.

11

Redox reaction

The oxidation and reduction reactions that move electrons from donor to acceptor molecules.

3

Reduction

A chemical reaction in which a substance gains one or more electrons.

3

Reduviid

A large winged insect that feeds on sleeping hosts in the evening hours.

25

Re-emerging infectious disease

A disease that was thought to be under control through the administration of antibiotics but reappears in the form of drug-resistant disease. A good example is tuberculosis.

8

Refractory septic shock

An irreversible, fatal hypotension caused by septic shock.

25

Regulatory T cell (Treg)

A T lymphocyte that regulates the cellular and humoral immune response.

16

Relapsing fever

Disease caused by Borrelia species. It is vector transmitted through tick or louse bites and has a poor prognosis, including severe jaundice bleeding and changes in mental status.

25

Replication fork

Location along the double-stranded DNA helix where replication is ongoing.

11

Replicator sequence

An easily opened sequence of A-T pairs in the DNA.

11

Resident (fixed) macrophages

Phagocytic cells that are stationed in specific tissues throughout the body.

15

Residual body

The exocytotic vesicle containing the elements of the destroyed organism. It is seen at the end of the phagocytic process.

15

Resistance islands

Areas of the chromosome in which there is an accumulation of genes associated with resistance to antimicrobial agents.

20

Reticulate body

The larger, more fragile, replicative form of Chlamydia.

23

Reticuloendothelial system

Old term for what is now known as the mononuclear phagocytic system.

15

Retrospective analytical study

A type of epidemiological study involving the analysis of data after the episode is over.

6

Retrovirus

An enveloped RNA virus that uses its own reverse transcriptase to transcribe its RNA into DNA in the cytoplasm of the host cell.

12

Reverse transcriptase

An enzyme found in retroviruses that can convert RNA into DNA.

6

Rheumatic fever

Febrile illness caused by infection with Group A hemolytic streptococci.

17

Rheumatoid arthritis

An autoimmune disease that occurs when the immune system attacks the synovial membrane of the synovial joints.

17

Rhinitis

Inflammation of the nasal mucous membranes.

21

Rhinorrhea

Discharge of thin nasal mucous.

21

Ribavirin

A broad-spectrum antiviral antibiotic used to treat severe viral pneumonia caused by respiratory syncytial virus, particularly in high-risk infants. Also used in conjunction with interferon for therapy of hepatitis C infection.

19

Ribose

The form of sugar found in RNA molecules.

2

Ribosomal RNA

The form of RNA that is part of the structure of the ribosomal subunits.

11

Ribosome

The structure in which translation of mRNA into proteins occurs.

4

Rice stool

Also known as rice water stool, a symptom of late stages of cholera infection, in which feces is likened to water from boiled rice.

22

Ring stage of malaria

Stage of malaria in which red blood cells are infected with merozoites, which take on a ring-like shape.

14

Ringworm

A skin lesion caused by fungi that can be found all over the body and is characterized by red margins, numerous scales and reddish itching skin.  

14

River blindness

Parasitic infection of the eye spread by the sucking blackfly, which causes corneal ulceration, fibrosis, and blindness.

26

RNAase H

The enzyme that removes the RNA primer from the fragments being made on the lagging strand of DNA during replication.

11

Rocky Mountain spotted fever

Disease caused by Rickettsia rickettsii, which is transmitted to humans by ticks.

25

Rostellum

Retractable chitinous hooks that are found on the scolex of tapeworms and are used for attachment.

14

Rubella

Also known as German measles. A viral infection characterized by a short-lived skin rash.

26

Rubeola

Also known as measles or hard measles. Common form of measles.

26

S pili

Fragments of pili intended to bind to and inactivate antibody molecules.

9

Saint Louis encephalitis

Type of viral encephalitis most often seen in humans in the central United States.

24

Salpingitis

Inflammation of the fallopian tubes.

23

Sanitization

Reducing microbial contamination to maintain or improve public health. For example, cleaning, disinfection, and removal of trash from public spaces.

18

Scalded skin syndrome

An infection caused by staphylococci that produces large patches of sloughed skin over the whole body.

26

Schistosome

A term used to describe the reproductive system of some flukes.

14

Schistosomiasis

Infection with the protozoan parasite Schistosoma.

14

Schizogony

A reproductive cycle of simple fission followed by sexual reproduction (gametogony).

14

Scolex

The head of the tapeworm used for attachment.

14

Sebaceous gland

Epidermal structure associated with hair follicles that secretes an oily substance called sebum.

26

Sebum

Oily substance secreted by the sebaceous glands.

15

Secondary immune response

The adaptive immune response that occurs when an antigen that has been previously seen is encountered again. This response is quicker and more powerful than the primary adaptive immune response.

16

Secondary infection

Infection that can occur in patients recovering from a primary infection. It can be worse than the primary infection because of the weakened immune response resulting from fighting off the primary infection.

7

Secondary syphilis

Middle-stage syphilis infection, characterized by a skin rash on the extremities.

23

Secretory piece

A protein found on the secretory IgA molecule that attaches it to mucins of the tissues.

16

Selectin

A molecule that is secreted from the epithelial cells of blood vessels that causes the margination of white blood cells at the site of the tissue damage.

15

Selective medium

Medium that encourages the growth of some organisms while inhibiting the growth of others.

6

Selective permeability

The ability to prevent the free passage of certain molecules and ions across the membrane while allowing others to pass through.

9

Selective toxicity

The ability of an antimicrobial agent to kill microbes without causing significant damage to the host.

19

Semi-continuous cell line

A cell line that survives for a moderate period of time before it must be started again from a tissue or organ.

13

Semi-synthetic penicillin

Natural penicillin that has been chemically modified in a laboratory.

19

Sensitivity

Detection limit of a diagnostic test.

6

Sepsis

 Presence in the blood of pathogenic microorganisms or their toxins.

25

Sepsis syndrome  

Sepsis that causes altered blood flow to organs.

7

Septa (singular septum)

Crosswalls seen in the hyphae of some molds and bacteria during formation of endospores.

9

Septic shock

A life-threatening hypotensive event caused by endotoxins, in which blood vessels collapse.

25

Septicemia

Rapid multiplication of pathogens in the blood.

6

Sequence

To determine the physical order and placement of bases in a molecule of DNA or RNA.

20

Serial dilution

Stepwise dilution of a concentrated solution repeatedly using the same dilution factor.

6

Serological

Referring to the diagnostic identification of antibodies in the patient serum.

6

Severe combined immunodeficiency syndrome (SCID)

A primary immunodeficiency congenital condition in which there is no T-cell function and no B-cell function.

17

Severe sepsis

Systemic inflammation due to infection.

7

Sexually transmitted urethritis

An infection that presents as dysuria, urethral discharge, or both.

23

Shiga toxin

A dangerous enterotoxin produced by Shigella organisms but also found in other Enterobacteriaceae that have acquired the genes for the production of the toxin.

22

Shigellosis

Also known as bacilliary dysentery. Gastrointestinal disease caused by several strains of Shigella that invade the intestinal tract.

22

Shingles

Sporadic disease caused by reactivation of varicella-zoster virus. It appears mostly in elderly and immunocompromised individuals.

7

Simple diffusion

The net movement of particles from a region of high concentration to a region of lower concentration. It requires no ATP.

9

Simple stain

A single dye used to reveal cell shapes and arrangements.

4

Single-stranded DNA (ssDNA) virus

A virus that possesses only one strand of DNA.

12

Sinusitis

Inflammation of the sinuses.

21

Sleeping sickness

Disease caused by the parasite Trypanosoma, also known as African trypanosomiasis. It is marked by intermittent and progressive loss of consciousness.

14

Slime layer

A thin protective structure loosely bound to the cell wall that protects some cells against drying and is sometimes used to bind cells together.

9

Slow infection

A type of persistent infection in which there is a prolongued incubation period before new virions are produced.

13

Smallpox

A formerly worldwide and serious viral infection that was declared eradicated.

5

Sodium thioglycolate

A reducing medium used for growing anaerobic bacteria.

10

Southern blot

Analytical tool to detect DNA in a sample.

6

Spanish influenza

An epidemic of influenza that occurred in 1918 and is believed to have killed 50 million people.

8

Specialized transduction

Type of transduction (transfer of genetic material) in which the DNA being transduced is limited to one or a few genes lying adjacent to the viral insert in the host chromosome that are accidentally included with the viral insert when it is excised from the host chromosome.

11

Specificity

Selectiveness of a diagnostic test.

6

Sphere of hydration

The surrounding of an ion with water molecules. It occurs because of the nonpolar covalent bonding seen in water molecules.

2

Spirillum (plural spirilla)

A spiral-shaped motile bacterium with a rigid cell.

4

Spirochete

A corkscrew-shaped motile bacterium with a flexible cell.

4

Spirochetemia

Spirochetes growing in the blood.

25

Splenomegaly

Enlargement of the spleen.

21

Spontaneous mutation

A mutation that occurs in the absence of any agent known to cause changes in DNA.

11

Sporadic disease

A disease that is limited to a small number of isolated cases, posing no threat to a large population.

6

Sporotrichosis

Fungal skin infection caused by Sporothrix schenckii and often transmitted to the body from plants.

14

Sporozoa

A group of protozoan parasites that use both sexual and asexual reproduction during infection.

14

Sporozoite

A malaria trophozoite present in the salivary glands of infected mosquitoes.

14

Sporulation

The formation of a spore.

4

Stationary phase of bacterial growth

The third of the four phases of the bacterial growth curve, in which new cells are produced at the same rate as the old cells die, leaving the number of live cells constant.

10

Sterilization

The killing or removal of all microorganisms in a material or on an object.

18

Stop codon

The last codon of mRNA to be translated at the ribosome, causing the release of the mRNA molecule.

11

Straintyping

Method for identifying strains of bacteria.

6

Strep throat

Serious infection of the pharynx by streptococcal bacteria.

21

Streptococcal toxic shock syndrome (STSS)

Toxic shock syndrome resulting from an infection with Streptococcus pyogenes.

7

Subacute disease

A disease that is intermediate between acute and chronic.

7

Subacute sclerosing panencephalitis

A progressive debilitating and fatal brain disorder caused by infection with a mutated measles virus.

13

Subclinical infection

An infection in which there are no apparent symptoms, either because there were insufficient organisms to produce them or because the immune response disposed of the infection before symptoms could appear.

7

Substrates

Substances acted upon by enzymes.

3

Subunit vaccine

A vaccine composed of immunogenic parts of virus derived from genetic engineering and recombinant DNA techniques.

13

Superantigen

Powerful antigens such as bacterial toxins that activate large numbers of T cells, causing a powerful immune response that can lead to toxic shock.

5

Supercoiling of DNA

The characteristic seen in DNA in which coils of the helix are themselves coiled. 

11

Superficial mycosis

Fungal infection that does not involve a tissue response.

14

Superinfection

A secondary infection caused by the loss of normal microbial flora, which permits colonization of the body by pathogenic and often antibiotic-resistant microbes.

20

Superorganism

A group of organisms, that functions as a whole unit.

7

Superoxide dismutase (SOD)

An enzyme that converts superoxide to molecular oxygen and hydrogen peroxide.

10

Suppressor mutations

Mutations reversing other previous mutations. 

11

Surfactants

Chemicals that reduce the surface tension of solvents. They are very effective for disrupting the plasma membrane of cells.

18

Swine flu

Influenza affecting pigs, or human influenza caused by a related virus.

8

Symptomatic phase of HIV infection

The end stage of the infection in which a variety of infections occur as a result of the loss of the patient’s immune defenses.

17

Symptoms of the disease

Characteristics such as headache and nausea that can be observed or felt only by the patient. These are nonmeasurable.

7

Syncytia

Multinucleate masses formed by the fusion of many virally infected cells into one gigantic cell.

5

Synercid antibiotics

Antibiotics containing a pair of antibiotics, quinupristin and dalfopristin.

19

Syphilis

Venereal disease caused by Treponema pallidum leading to many structural and cutaneous lesions.

4

Systemic autoimmunity

Autoimmune disease in which the immune response attacks multiple organs.

17

Systemic infection

An infection that occurs throughout the body.

7

Systemic lupus erythematosus (SLE)

An autoimmune disease in which autoantibodies are produced against DNA, RNA, and proteins associated with nucleic acids.  It causes damage to small blood vessels, especially in the kidneys.

17

T cell (T lymphocyte)

A thymus-derived lymphocyte involved in the adaptive immune response.

16

Tachycardia

Rapid heartbeat.

14

Tapeworms

Long ribbonlike helminths (worms). They are the largest of the intestinal parasites.

14

Tegument

The viral protein layer located between the capsid and the envelope in complex icosahedral viruses.

12

Teichoic acid

A polymer attached to peptidoglycan in Gram-positive cells.

9

Tertiary syphilis

Late-stage syphilis infection, characterized by localized lesions called gummas, as well as damage to the neurological and cardiovascular systems.

23

Tetanospasmin

The neurotoxic component of tetanus toxin.

24

Tetanus

An acute and often fatal infection caused by the neurotoxin produced by Clostridium tetani.

4

Tetanus toxin

A neurotoxin that inhibits the relaxation phase of muscle function.

24

Tetracycline

An antibacterial agent that inhibits protein synthesis.

19

TFH cells

TFH helper cells activate B cells, stimulating them to differentiate into plasma cells that produce antibody.

16

TH1 cells

TH1 helper cells activate macrophages to phagocytose and digest ingested microbes and to increase their number of MHC II molecules and cytokine receptors making them better antigen presenting cells.

16

TH2 cells

TH2 helper cells promote antiparasitic responses and allergic responses by activating eosinophils and mast cells.

16

TH17 cells

TH17 helper cells protect against extracellular bacteria and fungi by stimulating neutrophils.

16

Thermal death point (TDP)

The lowest temperature required to kill all the organisms in a sample in 10 minutes.

18

Thermal death time (TDT)

The shortest length of time needed to kill all organisms at a specific temperature.

18

Thermophiles

Bacteria that grow at high temperatures above 45°C.

10

Thrombocytopenia

A decrease in the number of platelets found in the circulating blood.

8

Thrombophlebitis

Inflammation of veins.

25

Thrush

Milky patches of inflammation on oral mucous membranes. It is a symptom of oral candidiasis caused by Candida albicans.

26

Tincture

A solution used to carry other antimicrobial chemicals.

18

Tinea capitis

Also called scalp ringworm. It is a form of ringworm in which hyphae grow in hair follicles, often leaving circular patterns of baldness.

14

Tinea corporis

Ringworm found between the fingers, in wrinkles in the palm, and on scaly skin.

14

Tinea cruris

Also called jock itch. It is groin ringworm that occurs in skin folds in the pubic area of the body.

14

Tinea nigra

Condition caused by the fungus Hortaea werneckii. Causes brown or black superficial skin lesions found mostly on the palms.

14

Tinea pedis

Also called Athlete's foot. It is a foot infection in which hyphae invade the skin between the toes, causing dry scaly lesions.

14

Titer

The amount or concentration of a substance in a solution.

6

Toll-like receptors

Molecules located on the surface of cells that defend the body. These receptors bind to antigens found on pathogens.

15

Tonsillitis

Inflammation of the tonsils in particular the palatine tonsils.

21

Topoisomerase

An enzyme that breaks the DNA chain, allowing supercoils to relax and strands of the double helix to separate, and then reseals the break.

11

Toxemia

The presence and spread of toxins in the blood.

7

Toxic shock syndrome (TSS)

Potentially fatal condition caused by superantigen exotoxins produced by Staphylococcus aureus and Streptococcus pyogenes. TSS produced by Staphylococcus aureus is often associated with the use of tampons.

5

Toxoid

An exotoxin that has been chemically inactivated but remains antigenic and can therefore be used to immunize against the toxin.

5

Tracheal toxin

The toxin produced by Bordetella pertussis. It immobilizes and progressively destroys ciliated cells.

21

Tracheobronchitis

Inflammation of the trachea and the bronchi.

21

Trachoma

A chronic conjunctivitis of the eye that leads to scarring, corneal ulceration, and eventual blindness.

26

Transcription

The process of producing RNA from DNA.

4

Transcriptomics

Discipline considering entire transcriptomes rather than individual mRNAs (transcripts).

6

Transcytosis

The movement of IgA across the epithelial cell barrier.

16

Transfer RNA

Type of RNA that transfers amino acids from the cytoplasm to the ribosome for placement into newly developing peptides.

11

Transferrin

A substance that binds iron.

15

Transformation

A form of transfer of genetic information in which naked DNA is taken up by recipient cells.

11

Translation

The synthesis of protein using the information carried by RNA.

11

Translational apparatus

The large and small subunits of ribosomal RNA and proteins, which come together to form the intact ribosome along with transfer and messenger RNA.

11

Translocation protein systems

Proteins in the cell that move substances out of the cell.

9

Transmissible spongiform encephalitis (TSE)

The neurological disease caused by prions.

8

Transmitted

In regards to a virus that is passed from one host directly to another host.

13

Transposition

The process in which genetic sequences can move from one location to another in the DNA.

11

Transposon

A mobile genetic sequence that contains the genes for transposition as well as one or more genes not related to transposition.

11

Trematode

A fluke.

14

Trench mouth

Also known as necrotizing periodontal disease and Vincent’s disease. A spectrum of acute inflammatory diseases resulting in the destruction of the soft tissue of the oral cavity.

22

Trichinosis

Disease caused by eating inadequately prepared meat infected with Trichinella spiralis. It is marked by diarrhea, nausea, fever, stiffness, and pain.

14

Trophozoite

The feeding and replicating stage of a protozoan.

14

Trypanosomiasis

A neurological disease caused by the parasite Trypanosoma. It is commonly referred to as African sleeping sickness.

14

Trypomastigote

The form of the parasite Trypanosoma that is found in the blood.

14

Tuberculosis

Severe infection of the lower respiratory tract, primarily caused by Mycobacterium tuberculosis.

1

Tumor necrosis factor (TNF)

A chemical cytokine seen in the inflammatory and immune response to infection.

15

Type 1 Insulin-dependent diabetes mellitus

An autoimme disease that results when the immune system attacks the insulin producing cells of the pancreas.

17

Typhoid fever

A form of enteric fever caused by Salmonella enterica serotype Typhi.

4

Typhoidal tularemia

Tularemia infection with symptoms similar to those of typhoid fever.

25

Ubiquitin

Molecular carrier tags for materials to be taken to the proteasome for recycling.

4

Ulcer

A defect or excavation of the surface of an organ or tissue produced by sloughing off of necrotic inflammatory tissue.

5

Ulceroglandular tularemia

A localized papule that forms at the inoculation site and becomes ulcerated and necrotized; caused by Francisella tularensis.

25

Undulant fever

A cycling pattern of symptoms seen in Brucellosis infections.

25

Urethritis

Inflammation of the urethra.

23

Uropathogenic

Causing disease in the urinary tract.

23

Use dilution method

A method used to determine whether a chemical substance is bacteriostatic or bacteriocidal.

18

Vacuolating cytotoxin

A circulating protein associated with Helicobacter pylori infections.

22

Vaginal candidiasis

A fungal infection of the vaginal area caused by the yeast Candida albicans.

23

Vaginitis

Inflammation of the vagina.

23

Valley fever

The disease caused by the infectious form of coccidioidomycosis.

21

Vancomycin-resistant enterococci (VREs)

Enterococcal organisms that are resistant to vancomycin.

20

Variable region of the antibody molecule

The most variable regions of the immunoglobulin molecule made up of variable regions of the heavy and light chain. It contains the antigen-binding site.

16

Variola major

A form of smallpox with a high mortality rate (20% or higher).

26

Variola minor

A form of smallpox with a low mortality rate.

26

Vasogenic edema

A swelling of the brain caused by albumin entering the cerebrospinal fluid.

24

Vector

An organism that transmits a disease-causing organism from one host to another.

7

Vector transmission

Movement of an organism from one host to another. This can be through biological mechanisms such as bites, or through mechanical mechanisms such as shedding from the vector’s body.

5

Vehicle transmission

The movement of a disease-causing organism through the use of a nonliving carrier.

6

Vesicles

(1) Membrane-enclosed inclusions in the cytoplasm of cells. (2) Type of skin lesion.

26

Vincent’s disease

Also known as necrotizing periodontal disease and trench mouth. A spectrum of acute inflammatory diseases resulting in the destruction of the soft tissue of the oral cavity.

22

Viral envelope

The structure seen around the capsid of some viruses. It is made up of the membrane components obtained when the mature virion leaves the host cell during the process of budding release.

4

Viremia

An infection in which viruses are transported in the blood but do not replicate there.

7

Virion

A mature fully developed viral particle.

12

Virucidal

Term describing a chemical agent that can kill viruses.

18

Virulence

The degree of fitness of the pathogen to overcome the body’s defenses and establish themselves.

1

Virulence factors

A structural or physiological characteristic that helps pathogens to establish themselves in the host.

1

VRSA

Vancomycin-resistant Staphylococcus aureus.

6

Wall teichoic acid

The form of teichoic acid that extends through only a portion of the Gram-positive cell wall of bacteria as opposed to all the way through.

9

Wart

Small growths characterized by thickening of the skin, which are caused by human papillomaviruses.

26

Watery diarrhea

The most common type of gastrointestinal infection symptom. It develops rapidly and results in frequent voiding.

22

West Nile meningoencephalitis

The most damaging form of West Nile virus infection with mild early symptoms similar to West Nile fever. It progresses to loss of consciousness, near coma, and hyperactive deep tendon reflexes that later diminish.

24

West Nile virus

A virus that causes an emerging infectious disease transmitted by mosquitoes. It causes problems of the central nervous system, including seizures and encephalitis.

24

Western Bolt

Analytical tool to detect protein in a sample.

6

Western equine encephalitis

Type of encephalitis seen most often in the western United States. It primarily affects horses but can also infect humans.

24

Whooping cough

A highly contagious respiratory infection caused by Bordetella pertussis. Also known as pertussis. Trophozoite

4

Widal reaction

Identifying an unknown antibody by using a known antigen.

6

Wiskott–Aldrich syndrome

A disease in which there are defects in the cytoskeleton of eukaryotic cells, causing a predisposition to infection with pyrogenic bacteria.

17

Wobble hypothesis

The theory developed by Francis Crick which states that errors in the third base of a codon can be acceptable because of the degeneracy of the genetic code.

11

X linked agammaglobulinemia

Primary immunodeficiency disease in which there is an absence of B cells leading to low levels of antibody production, which results in increased bacterial infection.

17

X-ray crystallography

A tool for examining the structure of molecules by examining the diffraction pattern created by beaming x-rays through a crystalline form.

20

Yeast

The single cell form of fungi.

14

Zone of inhibition

A clear area that appears on agar in the disk-diffusion method, indicating where the agent being tested has inhibited the growth of the organism.

18

Zoonotic disease

A disease that can be transmitted from animals to humans.

6

Zygomatic rhinitis

Fungal invasion of the tissue through the arteries causing areas of the mucosa to become grayish black (similar to a blood clot).

14