The hemolytic uremic syndrome rate seen in two years ago in Oklahoma’s outbreak of E. coli O111:NM was comparable to that typically seen in E. coli O157:H7-related outbreaks, according to a new study reported the current issue of the Archives of Internal Medicine.

Hemolytic uremic syndrome, or HUS, is a severe, life-threatening complication that occurs in about 10 percent of people who are infected with Shiga toxin-producing E. coli strains, including E. coli O157:H7 and E. coli O111. 

An unusual aspect to the largest outbreak of E. coli O111:NM ever experienced in the U.S. was that most of the HUS cases occurred among adults instead of children, the study found.

The study is based upon medical records of 341 patients who were infected with O111:NM after eating at a popular family-style restaurant in Locust Grove, OK called the Country Cottage in August 2008.

“HUS is not well described in non-O157 E coli outbreaks but occurs in 2 percent to 15 percent of O157 infections, predominantly among children,” the authors wrote.  “We examined outbreak-related hospitalizations to characterize E coli O111 illness, the HUS rate, and factors associated with subsequent HUS diagnosis among hospitalized patients.”

Authors of the O111 study are Dr. Emily W. Piercefield, federal Centers for Disease Control and Prevention’s Epidemic Intelligence Service Program assigned to the Oklahoma State Department of Health (OSDH); Dr. Kristy K. Bradley, and RNs Rebecca L. Coffman and Sue M. Mallonee, all with OSDH.

The study team found HUS was identified in 26 of the 156 (16.7 percent) confirmed or possible E coli O111 infections.  Dialysis was required in 65.4 percent of the patients with HUS, and one patient died.

Adults accounted for 57.7 percent of HUS cases with the age range being from 1 to 88 years for a median age of 43.

Upon admission to the hospital, patients that were later found to have HUS came in with high white cell counts, elevated serum creatinine levels and were vomiting.

The new study is the first inquiry into factors involved in the rare E. coli O111 outbreak since the OSDH final report on the outbreak.  Among the conclusions of that report were:

– A point-source outbreak originated from the Country Cottage restaurant in Locust Grove, Oklahoma.

– It could not be conclusively determined how E. coli O111:NM was introduced into the restaurant because E. coli was not isolated from any environmental specimen

– Although an exact mode of transmission for E. coli O111:NM was not identified, epidemiologic analysis suggested there was ongoing foodborne transmission of E. coli to Country Cottage customers between August 15 and August 24, 2008.

E. coli O111 was not isolated by bacterial culture methods or identified by molecular methods in any of them.  In the absence of finding the outbreak organism in any food handler or environmental specimen, how E. coli O111 entered the restaurant and was spread over numerous consecutive days is unclear. 

Apart from whatever mode the bacteria was introduced into the restaurant, the epidemiologic findings suggest a foodborne transmission of E. coli.

E. coli O111, through various food items–either contaminated with the bacteria by food handlers or by cross-contamination from food preparation equipment, counter surfaces, or storage areas–occurred at the County Cottage.