Pathogens

Question 1

Categories of disease

Answer 1

Infectious disease:
* Result from the pathogen’s growth

Intoxications:
* Result from the presence of a specific toxin

Question 2

Pathogen

Answer 2

Microbial parasites that are able to cause infection
* identified by the set of virulence genes that are carried and expressed

Question 3

Infection

Answer 3

Situation where microorganism is established & growing in host, causing damage

Question 4

Disease

Answer 4

Damage/injury to the host that impairs host function

Question 5

Pathenogenicity

Answer 5

Ability of a parasite to inflict damage to the host

Question 6

Virulence

Answer 6

Measure of pathogenicity

Question 7

Opportunistic pathogen

Answer 7

Cause disease only in absence of normal host resistance

Question 8

Virulence

Answer 8

Measure of the ability to cause damage

Determined by 2 features:
* Invasiveness
* Toxigenicity

Question 9

Invasiveness

Answer 9

Ability to become established, overcome defenses, & spread in tissues

Question 10

Invasiveness Virulence factors

Answer 10

• Adhesins
• Capsule
• Enzymes that destroy host tissues
• Invasins
• Type 3/4 Secretion Systems

Question 11

Adhesins

Answer 11

Promote specific attachment to the host cell surfaces
* Fimbriae/pili mediate loose attachment
* Afimbrial adhesins mediate close attachment

Question 12

Capsule

Answer 12

Prevents pathogen from being destroyed by host immune cells

Question 13

Enzymes that destroy host tissues

Answer 13

Hyaluronidase:
* Degrades hyaluronic acid (holds host cells together)

Collagenase:
* Degrades the protein collagen present in connective tissues

Lecithinase:
* Degrades lecithin in cell membrane
* Lysis of RBCs and tissue cells

Hemolysins:
* Enzymes and cytolysins (pore-forming)
* Cause RBC & tissue lysis

Question 14

Invasins

Answer 14

Surface/injected proteins that allow microorganisms to enter cells

Question 15

Type 3/4 Secretion Systems

Answer 15

• Invasion of host cells
• Block phagosome maturation
• Take control of host cells

Question 16

Toxigenicity

Answer 16

Capacity to produce toxins that damage specific tissues of the host

Question 17

Toxin categories

Answer 17

• Exotoxins
• Endotoxins

Question 18

Exotoxins

Answer 18

• Secreted into the surrounding as the bacterial pathogen grows
• Highly antigenic
• Heat-labile
• Usually proteins
• Categorized by their target

Question 19

Exotoxins examples

Answer 19

• Extracellular enzymes: Degrade host cells
• AB toxins: Modify host cells

Question 20

AB toxins

Answer 20

Subunit A:
* modifies target inside host cell leading to damage to the host

Subunit B:
* binds specific cell receptors providing tissue/cell type specificity

Question 21

AB Toxins: Cholera toxin

Answer 21

Subunit A:
* adenylate cyclase, produce cAMP

Subunit B:
* bind to intestinal cells

Question 22

Endotoxins

Answer 22

• Part of the bacterial pathogen
• Weakly antigenic
• Heat-stable
• Very effective activator of the immune system
• Produce general systemic effects (fever, inflammation)

Question 23

Vaccines against toxins

Answer 23

Exotoxins
* Toxins inactivated to toxoids by heat/formaldehyde
* Toxoids are no longer toxic, but still antigenic

Endotoxins:
* Cannot be inactivated to toxoids – no vaccines