O157

Escherichia coli O157 refers to a serogroup of the bacterium Escherichia coli. The most well known pathogenic member is Escherichia coli O157:H7, a member of the enterohemorrhagic E. coli (EHEC) group. The O antigen designates a surface polysaccharide and the H antigen designates a flagellar protein; O157:H7 is the classic combination associated with severe illness. O157 strains are notable for producing Shiga toxins that can damage the lining of blood vessels.

Infections typically cause abrupt abdominal cramps, diarrhea that often becomes bloody, vomiting, and mild fever. In some patients, particularly children and older adults, the illness can progress to hemolytic uremic syndrome (HUS), a serious condition that can cause kidney damage and failure. Most cases are self-limited, but severe complications can occur.

Transmission occurs by ingesting contaminated food or water, or through contact with animals or their environments. Common sources include undercooked ground beef, unpasteurized dairy products, contaminated fresh produce, and cross-contamination in the kitchen. Reservoirs are primarily cattle and other ruminants; humans can spread the organism to others.

Diagnosis is usually based on stool testing, including culture and detection of Shiga toxin genes (stx1, stx2). Some laboratories use sorbitol-containing selective media to identify O157:H7. Treatment is predominantly supportive, with careful hydration and electrolyte management; antibiotics are generally avoided in suspected EHEC infections due to concerns about toxin release and increased risk of HUS. Severe cases may require renal support.

O157 has had a significant public health impact with outbreaks worldwide since the 1980s. Prevention focuses on proper cooking, pasteurization, preventing cross-contamination, thorough washing of produce, and good hand hygiene.