First Aid - Bacterial Toxins/Virulence Factors, Resistance Mechanisms


Terms in this set (...)

1. Antiphagocytic virulence factor
2. Quelling reaction
3. S pneumo, HiB, N mening, Salmonella, Klebs, GBS
Protein A (s. aureus)
1. Factor binds Fc region of Ig
2. Prevents opsonisation and phagocytosis
IgA protease
1. Enzyme secreted by S pneumo, HiB, Niesseria (SHiN)
2. Respiratory mucosal colinsation
M protein
Helps prevent phagocytosis in group A strep
1. Lipopoysaccharide from cell membrane - structural part of bacteria that is released when the cell is lysed.
2. Induces TNFa, IL-1 > shock
3. Stable at 100 degrees Celsius for 1 hour
Diptheria toxin
1. Inactivates elongation factor (EF-2)
2. Causes pharyngitis and pseudomembrain in throat
3. AB-toxin
Pseudomonas Aeruginosa
1. Inactivate Elongation factor (EF-2)
2. Exotoxin A (AB-Toxin) - Causes host cell death
Shiga/Shiga-like toxin
Enterohemorrhagic E.coli (EHEC)
1. Inactivates 60S ribosome by RNA cleavage
2. Causes dysentery (mucus + blood) and HUS
Heat-Labile Toxin (e coli) - ETEC
1. Activates adenyl-cyclase = ^cAMP = ^Chloride secretion
2. Watery diarrhea
3. AB-Toxin

Labile in the Air, Stable on the Ground (Adenylate Cyclase)
Heat-Stable Toxin (e coli, yersinia)
1. Activates guanylate-cyclase = ^cGMP = Decreased resorption
2. Watery diarrhea

Labile in the Air, Stable on the Ground
Anthrax toxin
1. Mimics adenyl-clylase = Edema Factor
2. Black escar with edematous border
Cholera toxin
1. Activates Gs = ^adenyl-cyclase = ^cAMP = ^Cl excretion into gut and H2O efflux
2. Ricewater diarrhea
3. AB-Toxin
Pertussis toxin
1. Disables Gi = ^adenyl-cyclase = ^cAMP = impared phagocytosis permiting survival
2. AB-toxin
3. Whooping cough: Child coughs on expiration and whoops on inspiration (toxin may not be cause of cough)
Streptolysin O
1. Degrades cell membrane => RBC lysis - contributes to Beta-hemolysis
2. Antibody to this toxin diagnoses rheumatic fever
TSST-1 (Staph)/ Exotoxin A (Strep Pyogenes)
1. Brings MHC-II and TCR together = overwhelming INF-g and IL-2 = shock
2. Toxic Shock Syndrome - fever, rash, shock
S. aures and Strep. pyogenes
1. Blocks GABA release from renshaw cells
spastic paralysis
2. Cleave snare protein required for NT release
Botulinum toxin
1. Inhibits ACh release at NMJ
flacid paralysis
2. Cleaves snare protein required for NT release
Alpha-toxin (lecithinase)
1. Phospholipase that degrades tissue and cell membranes.
2. Causes gas gangreen - myonecrosis - and hemolysis (C. perfringens)
C. diff toxin A
Binds to gut brush border
C. diff toxin B
Destroys the cytoskeleton of enterocytes causing membrane formation
aminoglycoside resistance
transferase enzymes that inactivate drug by acetylation, phosphorylation or adenylation
tetracycline resistance
decreased uptake into cells or increased efflux out of cell by plasmid encoded transport pup
macrolide resistance
methylation of 23s rRNA binding site
chloramphenicol resitance
plasmid-encoded acetyltransferase that inactivates drug
sulfonamide resistance
altered enzyme (bacterial dihydropteroate synthase), decreased uptake or increased PABA synthesis
fluoroquinolone resistance
chromosome-encoded mutation in DNA gyrase, plasmid-mediated resistance, efflux pumps
vancomycin resistance
D-ala D-ala to D-ala D-lac
penicllin, ampicillin, amoxicillin resistance
beta-lactamases cleave ring
cephalosporin resistance
change in structure of PCP that prevents cephalosporin binding
rifampin resistance
mutation in DNA-dependent RNA polymerase