Flashcards in Enterobacteriaceae I Deck (40)
Are enterobacteriaceae gram+ or -?
What are antibodies formed against in enterobacteriaceae?
O antigen of LPS
What part of LPS is responsible for toxicity?
Lipid A (causes fever, diarrhea, shock)
Where is the H antigen located?
Where is the K antigen located?
(causes UTI, invasive disease)
What are the 7 virulence factors for enterobacteriaceae?
1) Endotoxins (LPS)
2) Capsule (no phagocytosis)
3) antigenic phase variation
4) type III secretory system
5) sequestration of growth factors (ex: iron)
6) resistance to serum killing
7) antimicrobial resistance
Are enterobact obligative or facultative?
What key enzyme are enterobact NEGATIVE for?
What is the energy source for enterobact?
reduce nitrate to nitrite
Do all bacteria ferment lactose?
NO, some do and some don't
What is special about macconkey agar?
only gram NEGATIVE grow on it
What color do lactose fermenters turn on macconkey agar?
Is the normal flora in our body lactose positive or neg?
positive (streak a stool sample and if everything is purple, no infection)
What are the 7 tribes of enterobacteriaceae?
What is the most common enterobacteriaceae isolated from human infection?
Where is E. coli found in the environment?
if it is found in water, it is indicative of fecal contamination
What are 6 clinical syndromes that E. coli can cause?
1) gram negative sepsis
3) wound infection
4) pneumonia in IC hospitalized patients
5) meningitis in neonates
What are the 5 strains of E. coli causing gastroenteritis?
1) Enterotoxigenic (ETEC)
2) Enteropathogenic (EPEC)
3) Enteroinvasive (EIEC)
4) Enterohemorrhagic (EHEC)
5) Enteroaggregative (EAggEC)
What strain of E. coli is associated with Traveler's diarrhea? (profuse watery diarrhea)
What strain of E. coli is associated with infantile diarrhea?
EPEC (no gross blood)
What kind of E. coli is associated with blood, mucus, and many leukocytes in the stool? And tenesmus
EIEC (invade epithelial cells)
What kind of E. coli is associated with bloody diarrhea without WBCs? no fever
EHEC (caused by O157:H7)
What kind of E. coli is associated with watery diarrhea with blood and mucus, less commonly associated with abdominal pain?
What is the most common Shiga Toxin Producing E. coli (STEC)?
How is STEC transmitted?
feces of cattle, deer, sheep
humans get it via food (undercooked ground beef), water or direct contact with infected patient
What 2 infections are associated with E.coli O157?
- Hemolytic Uremic Syndrome (HUS)
- Hemorrhagic Colitis
What 3 things are indicative of hemorrhagic colitis?
1) abdominal cramps, watery diarrhea, bloody discharge
2) no significant fever
3) absence of WBC in stool
What is the triad of symptoms in HUS?
- acute renal failure
- hemolytic anemia
What is the leading cause of renal failure in kids?
(preceded by bloody diarrhea)
What is the clinical trajectory followed by Enterohemorrhagic E. coli?
3-4 days nonbloody diarrhea w/ ab pain then bloody diarrhea w/ severe ab pain
either resolves in 4-10 days or HUS
What does a CBC look like for an O157 E. coli patient?
RBCs are hypochromic (white) and fragmented (shisotcytes)
What is responsible for toxicity seen in O157?
shiga toxin (builds up on kidney wall)
What is the mechanism of action of Shiga toxin?
1) inhibit protein synthesis targets (of commensals and host cells)
2) damage microcirculation --> vasculitis --> mucosal damage
3) trigger signaling cascades (influence cytokines)
4) Hits endothelial and epithelial cells of the CNS
What 2 settings can HUS occur in?
1) diarrheal related (classical)
2) non-diarrheal HUS (pneumococcal infection, chemo, transplant immunosuppression)
What are 3 host risk factors that can increase chance of getting HUS?
1) young or old age
2) mental retardation
3) P antigen on RBCs (attachment site for shiga)
Treatment with what can worsen an O157 infection?
anti-motility agents (increase susceptibility)
True or false: serotypes other than O157 can cause disease
TRUE (still make shiga)
What antigens are you looking for to diagnose positive O157 infection?
O157 antigen (LPS)
What antibiotics do you treat STEC with?
NONE - will cause massive destruction of e. coli which will release all the shiga toxin and endotoxin