ID 4 Flashcards
c perfringens toxin
alpha toxin
alpha toxin mechanism
phospholipase (lecithinase) that degrades tissue and cell membranes
Alpha toxin manifestation on agar
hemolytic “double zone” of hemolysis on blood agar
what does alpha toxin lead to?
myonecrosis (“gas gangrene”)
strep pyogenes toxin?
streptolysin O
streptolysin O MOA
protein that degrades cell membrane, thus lysing RBCs
what do you use to diagnose ARF?
antistreptolysin o antibodies (ASO)
staph aureus toxin?
Toxic shock syndrome toxin (TSST-1)
strep pyogenes toxin?
Exotoxin A
TSST-1/exotoxin A MOA?
Bind to MHC II and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN gamma, and TNF-alpha –> shock
staph aureus toxin causing scalded skin syndrome?
exfoliative toxin
staph aureus toxin causing food poisoning?
enterotoxin
LPS components
O antigen + core polysaccharide + lipid A
How is endotoxin released?
Upon cell lysis or *by living cells by blebs detaching from outer surface membrane.
main effects of endotoxin
1) macrophage activation (TLR4)
2) complement activation
3) tissue factor activation
* extremely heat stable
what other cytokine contributes to fever?
TNF-alpha
Macrophage cytokines causing hypotension?
TNF-alpha + nitric oxide
endotoxin and DIC mechanism
endotoxin –> tissue factor activation –> coagulation cascade –> DIC
how do you differentiate between alpha and beta-hemolysis on culture?
beta-hemolytic shows a clear area surrounding colony (see FA 119)
food poisoning scenario for staph aureus and why
Rapid-onset food poisoning. It’s preformed toxin that has a short incubation period (2-6 hr)
What is MRSA resistant to?
methicillin and *nafcillin because of altered penicillin-binding protein
Labs in staphylococcal toxic shock syndrome
1) increased AST + ALT
2) increased bilirubin
Differentiating staphylococcal toxic shock syndrome from streptococcus pyogenes TSS
1) staphylococcal presentation = fever + vomiting + rash + desquamation + shock + end-organ failure.
2) strep pyogenes toxic shock-like syndrome = painful skin infection
S aureus food poisoning presentation
Non bloody diarrhea and emesis
Problem with s aureus food poisoning
It’s a heat stable enterotoxin that isn’t destroyed by cooking.
What is a staph abscess?
staph forms a fibrin clot around it’s itself.
saprophyticus appearance
cocci in clusters
Where is saprophyticus normally found?
Flora of female genital tract and perineum.
second most common cause of uncomplicated UTI in young women?
saprophyticus
Cause of sepsis in patients with sickle cell disease?
strep pneumo
virulence factor of strep pneumo?
Capsule. Without it’s capsule, strep pneumo is not virulent.
sputum with strep pneumo?
“rusty”
viridans group streptococcus causing endocarditis
s sanguinis (sanguinis means blood)
how do viridans group adhere to valves?
makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves.
scarlet fever toxin
erythrogenic toxin
How do you test for GBS
1) produces CAMP factor, which enlarges the area of hemolysis formed by S aureus (*NOT cAMP)
2) Hippurate test positive
GBS prophylaxis?
intrapartum penicillin
streptococcus bovis structure
gram positive cocci
what is s gallolyticus?
S bovis biotype 1
enterococci?
E faecalis
E faecium
VRE
where are enterococci found?
normal colonic flora
enterococci characteristisc?
penicillin G resistant
VRE primary concern?
impt cause of nosocomial infection
enterococci cause…
1) UTI
2) biliary tract infections
3) subacute endocarditis (*following GI/GU procedures)
enterococci testing…
1) PYR positive
2) variable hemolysis
3) can grow in 6.5% NaCl
4) can grow in bile
enterococci structure
Gram positive cocci in chains
Unique thing about bacillus anthracis
Only bacterium with a polypeptide capsule (contains D-glutamate)
cutaneous anthrax..
rarely progresses to bacteremia and death.
cutaneous anthrax description
painless papule surrounded by vesicles that leads to ulcer with black eschar (painless, necrotic)
pulmonary anthrax pathogenesis
inhalation of spores –> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.
