An 18-month-old girl develops pallor, oliguria, and lethargy 5 days after an episode of bloody diarrhea. Hemoglobin is 6.8 g/dL, platelets are 42 × 10^9/L, creatinine is 1.9 mg/dL, LDH is elevated, and peripheral smear shows fragmented red cells and helmet cells. What is the most likely causative organism?

• A Shiga toxin producing Escherichia coli O157:H7 ✓
• B Streptococcus pneumoniae
• C Salmonella typhi
• D Adenovirus type 11

Explanation

The triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury following bloody diarrhea defines typical diarrhea associated hemolytic uremic syndrome, most commonly caused by Shiga toxin producing E. coli O157:H7 and Shigella dysenteriae type 1. Antibiotics are generally avoided as they may increase toxin release. Pneumococcus causes a rare neuraminidase associated form, and adenovirus causes hemorrhagic cystitis, not HUS.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.