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/mu L (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.