Pathogenicity and Infection

Question 1

Primary Pathogen

Answer 1

Causes disease by direct interaction with healthy host.

Question 2

Opportunistic Pathogen

Answer 2

Part of the normal flora and causes disease when it has gained access to new tissues or the host has been compromised.

Question 3

Virulence Factors

Answer 3

Allow a pathogen to outcompete its host cells and resist their defenses. Determine the degree to which a pathogen causes infection.

Question 4

Infectious Process

Answer 4

Reservoir -> Entry -> Find/Establish Safe Environment -> Acquire Nutrients -> Establish Niche -> Exit (New host)

Question 5

Toxin

Answer 5

Specific substance that damages host.

Question 6

Toxemia

Answer 6

Condition caused by toxins in blood of host.

Question 7

Course of Infectious Disease

Answer 7

Incubation Period (after entry, before signs/symptoms)
Prodromal Stage (onset of signs/symptoms)
Period of Illness (Signs/symptoms most severe)
Convalescence (Signs/symptoms begin to disappear)

Question 8

Virulence

Answer 8

Intensity of pathogenicity.

Question 9

Pathogenicity Islands

Answer 9

Major virulence factors on large segments of chromosomal or plasmid DNA. Increase virulence.

Question 10

Adherence

Answer 10

After the pathogen has gained entry to host organism, adhesins help it to bind receptor sites on host cell surface.

Question 11

Colonization

Answer 11

Site of microbial reproduction on/in host. Doesn’t usually cause damage to host.

Question 12

Invasion

Answer 12

The spread of pathogen to other tissues within host. Once in circulatory system, pathogens have access to all organs. Bacteria in blood = bacteremia; Pathogens/toxins in blood = septicemia.

Question 13

Penetration

Answer 13

Active: Lytic substances which attack, degrade, and disrupt host cells.
Passive: Specific enzymes promote spreading to deeper tissues.

Question 14

Exotoxins

Answer 14

Mostly from Gram (+) cells; Among most lethal substances known; highly immunogenic; stimulate production of neutralizing antibodies.

Question 15

AB Exotoxins

Answer 15

Two subunits: A (cytotoxic effect) and B (binds to target).

Question 16

Superantigens

Answer 16

Stimulate T cells of immune system, causing them to overexpress and release cytokines.

Question 17

Endotoxins

Answer 17

Weakly immunogenic. Endogenous (part of) to pathogen. i.e. Lipid A of LPS in Gram (-) cell walls.

Question 18

Biofilm Development

Answer 18

Increases virulence, protects against antibiotics, and can lead to chronic infections.

Question 19

Resisting Host Defenses

Answer 19

Infect immune cells; fuse with adjacent cells to limit exposure to antimicrobial proteins; encapsulation to prevent phagocytosis; mutation in antigenic sites; produce substances that mimic host; produce proteases to degrade host proteins; produce proteins to interfere with host defenses.

Question 20

Pathogen Transmission

Answer 20

Airborne, Contact, Vehicle, Vector borne, and Vertical.

Question 21

Infectious Dose

Answer 21

ID50. Number of pathogens that will infect 50% of a group in a specified time.

Question 22

Lethal Dose

Answer 22

LD50. Number of pathogens that will kill 50% of animals in a group in a specified time.

Question 23

Cytopathology

Answer 23

Use tissue cultures to determine death rates rather than entire organisms.