E. coli!! MICROM 442 Deck 20 Flashcards

1
Q

E.coli is GM + or -?

A

GM-

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2
Q

does ecoli ferment lactose?

A

yes

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3
Q

is ecoli indole positive or negative

A

positive

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4
Q

what type of anaerobe is ecoli?

A

facultative

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5
Q

what type of pathogen is ecoli?

A

enteric

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6
Q

ecoli is the predominant GM- facultatively anaerobic bacteria in?

A

human GI tract

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7
Q

which settings is ecoli found where it is mmutualistic and lacks virulence?

A

soil, vegetables, water, undercooked meat

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8
Q

IPEC = intestinal pathogenic ecoli. symptoms =

A

diarrhea with onset more than 16 hrs after ingestion

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9
Q

ExPEC: extraintestinal pathogenic E. coli, symptoms =

A

UTI, bacteremia, pneumonia, peritonitis, meningitis

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10
Q

nosocomial infection: hospitals and long-term care

A

-catheter associated UTI [CAUTI]
- ventilator associated pneumonia [VAP] due to gastric aspiration
community acquired pneumonia [CAP] much less common

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11
Q

pathogenic ecoli has two branches which are?

A

ExPEC and IPEC

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12
Q

ExPEC varieties

A

UPEC
NMEC, SEPEC, APEC, MPEC

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13
Q

IPEC varieties

A

EPEC,
EHEC, ETEC
EAEC, DAEC, EIEC

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14
Q

IPEC: Acquisition of virulence determinants enables pathogenesis

A
  • adhesion
  • invasion
  • reduction of infectious dose
  • toxin production
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15
Q

ExPEC virulence onset

A

Translocation outside GI tract; capsule production

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16
Q

UPEC uropathogenic E. coli

A

Most common extraintestinal site of infection; second most common cause of hospitalization
behind pneumonia; most common underlying infection leading to bacteremia

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17
Q

UPEC virulence attributes

A
  • 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
18
Q

UPEC Predisposition to occurrence?

A
  • proximity of urethra to GI tract;
  • length of urethra;
  • minor trauma;
  • instrumentation [catheter];
  • outflow obstruction
19
Q

40% women will experience UTI; UPEC)

A
  • usually when sexually active
  • GI microbiota colonizing periurethral area
  • bladder of most women contain GI microbiota
    after intercourse;
  • most instances purged by urination
20
Q

ETEC enterotoxogenic E. coli = colonizing fimbria

21
Q

ST=

A

heat-stable peptide toxin; stimulates guanylate cyclase leading to increased
cAMP leading to Cl and water secretion and inhibition of NaCl uptake

22
Q

LT=

A

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]

23
Q

ETEC = the single most important cause of?

A

travelers diarrhea; infectious dose about 10e8;
contaminated food and water

24
Q

EHEC/STEC enterohemorrhagic/Shiga toxin producing E. coli =

A

intimin facilitates adhesion/colonization

25
EHEC/STEC has shiga toxin which has two types
Stx1 and Stx2
26
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
27
abscence of which strain does NOT cause bloody diarrhea
Stx2
28
encodes pore-forming toxin EHEC-hemolysin
pO157
29
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
30
triad of thrombocytopenia, anemia, renal insufficiency associated with EHEC/STEC
Hemolytic Uremic Syndrome (HUS)
31
E.coli diarrheal outbreaks associated with?
ontaminated produce, raw dairy products, undercooked beef
32
99% cattle in feed lots are positive for EHEC but they are not susceptible to?
the shiga toxin
33
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
34
Dx of E.coli
-GNR on Gm stain -isolate by culture on MacConkey plates (LACTOSE fermenter) -indole positive
35
O157
-H7 ferments sorbitol [MacConkey Sorbitol plates] -BUT some O157 have also been identified that do no ferment sorbitol
36
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
37
Rx =
Prevention based on sanitation, dietary discretion, avoiding extraintestinal translocation of bacteria
38
Abx dosage is based on typically?
local antibiograms
39
Resistant to typically what abx?
- ESBL [extended spectrum beta lactamases] - carbapenemase-producing strains
40
E.coli watery diarrhea treatment -> PEPTO baby :D
- rehydration - bismuth-subsalicylate - loperamide [anti-motility] - antibiotics rarely necessary
41
ecoli bloody diarrhea treatment
- rehydration - bismuth-subsalicylate - loperamide [anti-motility] - antibiotics rarely necessary