Enterohemorrhagic Escherichia coli (EHEC)

Question 1

What similarity does EHEC have with EPEC?

Answer 1

EHEC has a set of EPEC genes (called eae genes), so it produces an attaching effacing lesion.

Question 2

What is a difference between EHEC and EPEC?

Answer 2

EHEC produces a toxin that can lead to hemolytic uremic syndrome (which is much more serious)

Question 3

Steps of adherance of EHEC

Answer 3

1) Bundle-forming pili (Bfp) assist in adherence from relatively long distance
2) Syringe-like secretion system (called type III secretion) injects Tir into host cell
3) Tir binds to intimin on E. coli, resulting in pedestal formation
(same steps as EPEC)

Question 4

What toxin does EHEC produce?

Answer 4

Shiga-like toxin (aka Vero toxin)

Question 5

What does shiga-like toxin attack?

Answer 5

Small blood vessels in the large intestine

Question 6

What are the effects of inflammation on shiga-like toxin?

Answer 6

Shiga-like toxin activity intensifies in the presence of inflammatory cytokines

Question 7

Why is treatment of EHEC with antibiotics controversial?

Answer 7

The CDC says no antibiotics. Antibiotics cause degradation of E. coli, which releases cytokines. Cytokines increase inflammation, which will increase the activity of shiga-like toxin

Question 8

Besides inflammatory colitis, what other condition can result from an EHEC infection? What organ is affected?

Answer 8

Inflammation can cause for shiga-like toxin to affect the kidneys and cause nephritis.