E. coli!! MICROM 442 Deck 20 Flashcards
E.coli is GM + or -?
GM-
does ecoli ferment lactose?
yes
is ecoli indole positive or negative
positive
what type of anaerobe is ecoli?
facultative
what type of pathogen is ecoli?
enteric
ecoli is the predominant GM- facultatively anaerobic bacteria in?
human GI tract
which settings is ecoli found where it is mmutualistic and lacks virulence?
soil, vegetables, water, undercooked meat
IPEC = intestinal pathogenic ecoli. symptoms =
diarrhea with onset more than 16 hrs after ingestion
ExPEC: extraintestinal pathogenic E. coli, symptoms =
UTI, bacteremia, pneumonia, peritonitis, meningitis
nosocomial infection: hospitals and long-term care
-catheter associated UTI [CAUTI]
- ventilator associated pneumonia [VAP] due to gastric aspiration
community acquired pneumonia [CAP] much less common
pathogenic ecoli has two branches which are?
ExPEC and IPEC
ExPEC varieties
UPEC
NMEC, SEPEC, APEC, MPEC
IPEC varieties
EPEC,
EHEC, ETEC
EAEC, DAEC, EIEC
IPEC: Acquisition of virulence determinants enables pathogenesis
- adhesion
- invasion
- reduction of infectious dose
- toxin production
ExPEC virulence onset
Translocation outside GI tract; capsule production
UPEC uropathogenic E. coli
Most common extraintestinal site of infection; second most common cause of hospitalization
behind pneumonia; most common underlying infection leading to bacteremia
UPEC virulence attributes
- adherence by Type 1 and P pili
- frequently encapsulated
- capable of invading superficial epithelial cells
- production of alpha-toxin
- CNF [cytotoxic necrotizing factor] disrupts intracellular signaling and cytoskeleton
UPEC Predisposition to occurrence?
- proximity of urethra to GI tract;
- length of urethra;
- minor trauma;
- instrumentation [catheter];
- outflow obstruction
40% women will experience UTI; UPEC)
- usually when sexually active
- GI microbiota colonizing periurethral area
- bladder of most women contain GI microbiota
after intercourse; - most instances purged by urination
ETEC enterotoxogenic E. coli = colonizing fimbria
ST and LT
ST=
heat-stable peptide toxin; stimulates guanylate cyclase leading to increased
cAMP leading to Cl and water secretion and inhibition of NaCl uptake
LT=
heat-labile toxin; classic AB subunit toxin; increases cAMP in gastrointestinal
epithelium leading to Cl and water secretion and inhibition of NaCl uptake [LT less
potent but similar to CT]
ETEC = the single most important cause of?
travelers diarrhea; infectious dose about 10e8;
contaminated food and water
EHEC/STEC enterohemorrhagic/Shiga toxin producing E. coli =
intimin facilitates adhesion/colonization
EHEC/STEC has shiga toxin which has two types
Stx1 and Stx2
what type of toxin is shiga?
lassical A-B subunit toxin
- B pentamer subunit bind glycosphingolipid Gb3 on enterocytes/endothelium
- A subunit inhibits protein synthesis
abscence of which strain does NOT cause bloody diarrhea
Stx2
encodes pore-forming toxin EHEC-hemolysin
pO157
EHEC/STEC
localized damage to GI epithelium allows systemic delivery of Stx
- toxicity for endothelial cells, especially in kidney [glomerulus, the filtration unit]
- generalized endothelial cell toxicity:
- activation of coagulation cascade and thrombosis
- thrombocytopenia
- anemia
triad of thrombocytopenia, anemia, renal
insufficiency associated with EHEC/STEC
Hemolytic Uremic Syndrome (HUS)
E.coli diarrheal outbreaks associated with?
ontaminated produce, raw dairy products,
undercooked beef
99% cattle in feed lots are positive for EHEC but they are not susceptible to?
the shiga toxin
infectious dose for humans=10e2
-24% children infected with Stx2-expressing EHEC/STEC get HUS
- 4% of children who develop HUS in this context will die
- 5% serious long term sequelae
- 20-30% develop other sequelae
- hypertension, proteinuria, and reduced glomerular filtration rate [all due to kidney damage]
- others recover in about 2 weeks
Dx of E.coli
-GNR on Gm stain
-isolate by culture on MacConkey plates (LACTOSE fermenter)
-indole positive
O157
-H7 ferments sorbitol [MacConkey Sorbitol plates]
-BUT some O157 have also been identified that do no ferment sorbitol
Dx of E.coli con.
Enteric pathogens multiplex nucleic acid test
- detects multiple GI pathogens
- includes all pathotypes: EPEC, ETEC, EHEC/STEC,
EAEC, EIEC/Shigella
Rx =
Prevention based on sanitation, dietary discretion,
avoiding extraintestinal translocation of bacteria
Abx dosage is based on typically?
local antibiograms
Resistant to typically what abx?
- ESBL [extended spectrum beta lactamases]
- carbapenemase-producing strains
E.coli watery diarrhea treatment -> PEPTO baby :D
- rehydration
- bismuth-subsalicylate
- loperamide [anti-motility]
- antibiotics rarely necessary
ecoli bloody diarrhea treatment
- rehydration
- bismuth-subsalicylate
- loperamide [anti-motility]
- antibiotics rarely necessary
