Which organism is associated with hemolytic uremic syndrome as a complication after infection?

• A. E. coli O157:H7
• B. Salmonella Typhi
• C. Vibrio cholerae O1
• D. Yersinia enterocolitica

Answer: (A)

Hemolytic uremic syndrome is most clearly linked to infection with Shiga toxin–producing Escherichia coli, especially the enterohemorrhagic strain E. coli O157:H7. After such an infection, the Shiga-like toxin injures the lining of small blood vessels, particularly in the kidneys, triggering platelet activation and formation of microthrombi. This leads to hemolytic anemia from red blood cell fragmentation, thrombocytopenia, and acute kidney injury—the classic triad of HUS. Other organisms listed cause other diseases (typhoid fever, cholera, gastroenteritis) and are not typically associated with HUS, making E. coli O157:H7 the best fit for this complication.