(II) Gram Negative Rods - (2)*Escherchia coli

Question 1

Characterize (5) : E. coli

Answer 1

(1) Gram (-) rod
(2) Lactose fermenter
(3) Capsule
(4) Catalase (+)
(5) Fimbriae

Question 2

What color does E. coli turn MacConkey agar?

Answer 2

Pink

Question 3

What are the lactose fermenting bacteria?

Answer 3

(1) E. coli
(2) Klebsiella
(3) Enterobacter
(4) Serratia

Question 4

What does E. coli’s K antigen represent?

Answer 4

Kapsule

Question 5

What color does E. coli turn eosin methylene blue agar?

Answer 5

Green

Question 6

What organism most commonly causes UTIs?

Answer 6

E. coli

Question 7

What organism is the leading cause of gram (-) sepsis?

Answer 7

E. coli

Question 8

Can all strains of E. coli cause neonatal meningitis?

Answer 8

No, requires** K** antigen

(Just like Haemophilus requires capsule antigen B and only encapsulated forms of Neisseria cause meningitis)

Question 9

ROT: EHEC

Answer 9

Eating undercooked hamburgers

Question 10

Name 2 signs/symptoms of EHEC

Answer 10

(1) Bloody diarrhea
(2) HUS ⇒ Hemodynamic collapse

(Note: Do NOT give antibiotics. Rapid release of toxin can lead to HUS)

Question 11

Which strain of E. coli does not ferment sorbitol?

Answer 11

EHEC

Question 12

What serotype is most associated with EHEC outbreaks?

Answer 12

O157:H7

Question 13

ROT: ETEC

Answer 13

Drinking contaminated water

(“Montezuma’s revenge”)

Question 14

MOA: ETEC’s 2 toxins

Answer 14

(1) Heat Labile: ↑ cAMP
(2) **Heat Stable: ↑ cGMP
**
(Heat labile toxin is similar to cholera toxin)

Question 15

What is the difference in GI symptoms of ETEC and EHEC?

Answer 15

(1) EHEC: Bloody diarrhea
(2) ETEC: Watery diarrhea

Question 16

E coli is a major cause of death through […]

Answer 16

E coli is a major cause of death through diarrhea

Its not the clinical presentation but the diarrhea and resulting dehydration that is the most lethal

Treat with ORS!

Question 17

What are the clinical presentations of E.coli infection? (VTEC/EHEC/STEC in particular) (vvvvv IMPT!!!)

• […]
• […]
• […]
• […]
• […]
• […]

Answer 17

What are the clinical presentations of E.coli infection? (VTEC/EHEC/STEC in particular) (vvvvv IMPT!!!)

• Urinary tract infections (number 1 cause) – especially those with abnormal anatomy e.g. urethral valves, stones, BPH, catheters etc
• Neonatal infections (septicaemia, meningitis) (number 2 cause. Number 1 is GBS)
• Gut-related Sepsis(post-operative, biliary)
• Nosocomial infections (together with the other enterobacteriaceae)
• Diarrhoeal disease (by strains which have acquired virulence determinants (EPEC, ETEC, EIEC, etc). Low infectious dose <100 organisms)
• VTEC/EHEC/STEC causes **hemorrhagic colitis (with bloody diarrhea), complicated by Haemolytic Uremic Syndrome HUS (acute renal failure, microangiopathic hemolytic anaemia, thrombocytopenia) (biggest cause of renal failure in children)

Shigatoxigenic Escherichia coli (STEC) = verotoxigenic E. coli (VTEC) = enterohemorrhagic E. coli (EHEC) (ALL SAME SAME)

If u are curious about the mechanism that leads to HUS, can watch sketchy microb~ Or look at my sketch? HAHHHA