Virulence Factors

Question 1

Protein A

Answer 1

S. aureus

Binds Fc region of IgG, prevents opsonization and phago

Question 2

IgA Protease (fxn, 3 bugs w/ it)

Answer 2

Cleaves IgA to colonize respiratory tract
SHiN
Strep pneumo
Hib
Neisseria

Question 3

Protein M, what bug, fxn, significance

Answer 3

Strep pyogenes
helps prevent phago
similar epitopes to humans = molecular mimicry

Question 4

Type III Secretion (what, function, 4 bugs)

Answer 4

Injectisome: needle-like protein that directly injects toxin
Gram -'s:
Shigella
Salmonella
E Coli
Pseudomonas

Question 5

Exotoxin

Answer 5

Secreted from cell
Genes located in plasmid/bacteriphage
High toxicity
Induces high-titer ab’s called anti-toxins
Can use toxoid as vaccine
Destroyed rapidily at 60 degree celsius (except staph enterotoxin)
Examples: tetanus, botulinum, diptheria

Question 6

Endotoxins

Answer 6

Found in most GN’s outer LPS
Generate strong immune response (i.e. sepsis)
Genes in bacterial chromosome

Question 7

Exotoxin that inhibits EF-2

Answer 7

1. Diptheria Toxin* (C. diptheria)

2. Exotoxin A* (Pseudomonas)

Question 8

Exotoxin that inhibits 60S ribosome by removing adenine from rRNA

Answer 8

1. Shiga toxin* (shigella)

2. Shiga-Like-Toxin* (EHEC)

Question 9

** toxin

Answer 9

AB ribosylating toxin
A: active site, binds ADP-ribosyl and causes damage
B: binding site, binds host for endocytosis

Question 10

Function of HL* ETEC

Answer 10

activates adenyl cylase → inc cAMP, inc Cl- secretion into gut and H20 efflux

Question 11

Function of HS ETEC

Answer 11

activates guanylate cycle → inc cGMP, dec NaCl absorption and increase H20 efflux

Question 12

Edema Toxin*

Answer 12

Bacillus anthracis

Mimics adenylate cycle anzyme, inc cAMP

Question 13

permanantly activates Gs receptor, inc cAMP

Answer 13

Cholera toxin*

“rice water stools”

Question 14

activates cAMP by inhibiting Gi (bug and result)

Answer 14

Pertussis Toxin* (bordatella pertussis)

-inhibits phagocytois, and allows for survival

Question 15

proteases that cleave SNARE proteins (required for NT release via vesicular fusion) - 2

Answer 15

1. Tetanospasmin*: inhibit GABA and Glycine release from Renshaw cells in spinal cord
2. Botulinum*: inhibit Ach release at NMJ

Question 16

Alpha Toxin * (bug, function, s/s)

Answer 16

C. perfringens
Toxin is a phospholipase (lecithinase) that degrades tissues and cell membranes
Break down PLs: myonecrosis + gas gangrene
Hemolysis: double zone of hemolysis on blood agar

Question 17

Streptolysin O (bug, fxn, s/s)

Answer 17

Strep pyogenes
Lyses RBCs, contributes to beta-hemolysis
Can use anti-SO (ASO) ab’s to dx RF

Question 18

Superantigen function

Answer 18

Binds MHC and TCR at site other than antigen binding site. Cause huge release of cytokines:
IL-1, IL-2, IFN-alpha, IFN-gamma → shock

Question 19

S aureus superantigens (3)

Answer 19

TSST-1 (toxic shock: fever, rash, shock)
Exfoliative toxin: scaled skin
Enterotoxin: food poisoning

Question 20

S pyogenes superantigen

Answer 20

Exotoxin A: fever, shock, rash

don’t confuse w/ pseudomonas Exotoxin A* - blocks protein synthesis

Question 21

5 toxins w/ gene transfer via speciallized, lysosomal phages

Answer 21

ABCDE

1. shigA-like toxin: SLT* (EHEC)
2. Botulinum* (certain strains)
3. Cholera toxin*
4. Diptheria toxin*
5. Erythrogenic toxin - i.e. S pyogenes Exotoxin A

Question 22

dipicolonic acid in the core

Answer 22

spore stage, can form at the end of stationary phase when nutrients are limited.
no metabolic activity

Question 23

whats required to kill spores

Answer 23

autoclave at 121 degrees celsius for 15 min

Question 24

3 species with spore forms

Answer 24

Bacillus
Clostridium
Coxiella burnetti (Q fever)

Question 25

C diff toxins (2, and function)

Answer 25

A toxin: enterotoxin, binds brush border
B toxin: cytotoxin, depolymerizes actin → disrupts cytoskeleton
lead to → pseudomembranous colitis and diarrhea

Question 26

2 common causes of pseudomembranous colitis

Answer 26

1. Clindamycin

2. Ampicillin

Question 27

Treatment of pseudomembranous colitis (acute and recurrent)

Answer 27

Metronidazole or oral vancomycin

Recurrent: Fidaxomicin or fecal transplant

Question 28

toxin in B. cereus food poisoning

Answer 28

cereulide