E. coli!! MICROM 442 Deck 20

Question 1

E.coli is GM + or -?

Answer 1

GM-

Question 2

does ecoli ferment lactose?

Answer 2

yes

Question 3

is ecoli indole positive or negative

Answer 3

positive

Question 4

what type of anaerobe is ecoli?

Answer 4

facultative

Question 5

what type of pathogen is ecoli?

Answer 5

enteric

Question 6

ecoli is the predominant GM- facultatively anaerobic bacteria in?

Answer 6

human GI tract

Question 7

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

Answer 7

soil, vegetables, water, undercooked meat

Question 8

IPEC = intestinal pathogenic ecoli. symptoms =

Answer 8

diarrhea with onset more than 16 hrs after ingestion

Question 9

ExPEC: extraintestinal pathogenic E. coli, symptoms =

Answer 9

UTI, bacteremia, pneumonia, peritonitis, meningitis

Question 10

nosocomial infection: hospitals and long-term care

Answer 10

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

Question 11

pathogenic ecoli has two branches which are?

Answer 11

ExPEC and IPEC

Question 12

ExPEC varieties

Answer 12

UPEC
NMEC, SEPEC, APEC, MPEC

Question 13

IPEC varieties

Answer 13

EPEC,
EHEC, ETEC
EAEC, DAEC, EIEC

Question 14

IPEC: Acquisition of virulence determinants enables pathogenesis

Answer 14

• adhesion
• invasion
• reduction of infectious dose
• toxin production

Question 15

ExPEC virulence onset

Answer 15

Translocation outside GI tract; capsule production

Question 16

UPEC uropathogenic E. coli

Answer 16

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

Question 17

UPEC virulence attributes

Answer 17

• 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

Question 18

UPEC Predisposition to occurrence?

Answer 18

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

Question 19

40% women will experience UTI; UPEC)

Answer 19

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

Question 20

ETEC enterotoxogenic E. coli = colonizing fimbria

Answer 20

ST and LT

Question 21

ST=

Answer 21

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

Question 22

LT=

Answer 22

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]

Question 23

ETEC = the single most important cause of?

Answer 23

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

Question 24

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

Answer 24

intimin facilitates adhesion/colonization

Question 25

EHEC/STEC has shiga toxin which has two types

Answer 25

Stx1 and Stx2

Question 26

what type of toxin is shiga?

Answer 26

lassical A-B subunit toxin
- B pentamer subunit bind glycosphingolipid Gb3 on enterocytes/endothelium
- A subunit inhibits protein synthesis

Question 27

abscence of which strain does NOT cause bloody diarrhea

Answer 27

Stx2

Question 28

encodes pore-forming toxin EHEC-hemolysin

Answer 28

pO157

Question 29

EHEC/STEC

Answer 29

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

Question 30

triad of thrombocytopenia, anemia, renal
insufficiency associated with EHEC/STEC

Answer 30

Hemolytic Uremic Syndrome (HUS)

Question 31

E.coli diarrheal outbreaks associated with?

Answer 31

ontaminated produce, raw dairy products,
undercooked beef

Question 32

99% cattle in feed lots are positive for EHEC but they are not susceptible to?

Answer 32

the shiga toxin

Question 33

infectious dose for humans=10e2

Answer 33

-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

Question 34

Dx of E.coli

Answer 34

-GNR on Gm stain
-isolate by culture on MacConkey plates (LACTOSE fermenter)
-indole positive

Question 35

O157

Answer 35

-H7 ferments sorbitol [MacConkey Sorbitol plates]
-BUT some O157 have also been identified that do no ferment sorbitol

Question 36

Dx of E.coli con.

Answer 36

Enteric pathogens multiplex nucleic acid test
- detects multiple GI pathogens
- includes all pathotypes: EPEC, ETEC, EHEC/STEC,
EAEC, EIEC/Shigella

Question 37

Rx =

Answer 37

Prevention based on sanitation, dietary discretion,
avoiding extraintestinal translocation of bacteria

Question 38

Abx dosage is based on typically?

Answer 38

local antibiograms

Question 39

Resistant to typically what abx?

Answer 39

• ESBL [extended spectrum beta lactamases]
• carbapenemase-producing strains

Question 40

E.coli watery diarrhea treatment -> PEPTO baby :D

Answer 40

• rehydration
• bismuth-subsalicylate
• loperamide [anti-motility]
• antibiotics rarely necessary

Question 41

ecoli bloody diarrhea treatment

Answer 41

• rehydration
• bismuth-subsalicylate
• loperamide [anti-motility]
• antibiotics rarely necessary