Escherichia coli O157:H7 is a disease-causing serotype of E. coli that can produce Shiga-like toxins. It is important to understand how it spreads, why it can cause severe illness, and which people are at greatest risk.
E. coli O157:H7 is a serotype of the bacterial species Escherichia coli and is among the Shiga-like toxin–producing E. coli (STEC). It is gram-negative and oxidase-negative. Unlike many other E. coli strains, it does not ferment sorbitol. This difference can help laboratories distinguish it from common sorbitol-fermenting strains.
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What is E. coli O157:H7?
A serotype of *Escherichia coli* that belongs to the Shiga-like toxin–producing *E. coli* group.
How does sorbitol non-fermentation help identify O157:H7?
O157:H7 does not ferment sorbitol, unlike many common *E. coli* strains; laboratories can use this trait to distinguish it.
What is a prophage?
Bacteriophage genetic material incorporated into a bacterial cell; it can carry genes associated with Shiga-like toxin production.
What is HUS?
Hemolytic–uremic syndrome, a serious complication involving red blood cell destruction and acute kidney failure.
Why are some cattle called super-shedders?
They excrete especially large amounts of O157:H7 and can contribute disproportionately to environmental contamination.
Quiz questions
On sorbitol-MacConkey agar, how do O157:H7 colonies typically appear?Answer: Clear, because the bacteria do not ferment sorbitol.
What does PCR detect when used to identify O157:H7 in a stool sample?Answer: Bacterial DNA after it has been extracted from the sample.
Why are antibiotics generally avoided for O157:H7 infection unless a clinician determines otherwise?Answer: They may trigger processes that increase toxin production and the risk of HUS.
Which groups are at increased risk of severe outcomes from O157:H7 infection?Answer: Young children, older adults, and people with compromised immune systems.
Which event helped establish O157:H7 as a human pathogen in 1982?Answer: An outbreak in Oregon and Michigan linked to contaminated hamburger patties.