Hemolytic Uremic Syndrome After an Escherichia coli O111 Outbreak.

BACKGROUND In August 2008, the largest known US serotype 1 Escherichia coli O111 outbreak occurred in Oklahoma, causing 341 illnesses, including hemolytic uremic syndrome (HUS). HUS is not well described in non-O157 E coli outbreaks but occurs in 2% to 15% of O157 infections, predominantly among children. We examined outbreak-related hospitalizations to characterize E coli O111 illness, the HUS attack rate, and factors associated with subsequent HUS diagnosis among hospitalized patients. METHODS Medical records were reviewed for clinical presentation and evidence of HUS among hospitalized patients identified during the outbreak investigation. Characteristics of hospitalized patients with vs without HUS were compared. RESULTS HUS was identified in 26 of 156 (16.7%) confirmed or probable E coli O111 infections; 65.4% of patients with HUS required dialysis, and 1 patient died. The median age of patients with HUS was 43.5 years (age range, 1-88 years); adults composed 57.7% of HUS cases. Characteristics at hospital admission associated with subsequent HUS diagnosis included white blood cell count of at least 20 000/μL (adjusted odds ratio [aOR], 11.3; 95% confidence interval [CI], 1.7-75.3), elevated serum creatinine level for age (9.7; 1.4-69.2), and vomiting before hospital admission (6.8; 1.5-31.3). Administration of antimicrobial agents (risk ratio [RR], 1.0; 95% CI, 0.5-1.8) or medication with antimotility effects (1.4; 0.6-2.9) was not associated with subsequent HUS. CONCLUSIONS The HUS attack rate in this E coli O111 outbreak was comparable to that for E coli O157-related illnesses, but most cases occurred among adults. On admission, factors associated with subsequent HUS can identify patients who require close monitoring and early aggressive supportive care to improve outcomes.