A 3-year-old child presents with acute onset of bloody diarrhea, followed 5 days later by pallor, petechiae, and oliguria. Peripheral smear shows schistocytes and fragmented RBCs. Platelet count is 40,000/cu mm. Blood urea is elevated. What is the most likely causative organism?

• A Streptococcus pneumoniae
• B Salmonella typhi
• C Clostridium difficile
• D Escherichia coli O157:H7 ✓

Explanation

This is typical hemolytic uremic syndrome (HUS): prodromal bloody diarrhea followed by microangiopathic hemolytic anemia (schistocytes), thrombocytopenia, and acute kidney injury. E. coli O157:H7 (Shiga toxin-producing) causes >90% of childhood typical HUS. Pneumococcus causes atypical HUS (not diarrheal). C. difficile causes pseudomembranous colitis. Salmonella causes enteric fever.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.