Jul 25, 2002 (CIDRAP News) – The outbreak of Escherichia coli O157:H7 infections linked with ground beef from a ConAgra packing plant in Greeley, Colo., has reached 28 cases in seven states, federal health officials said today in discussing their investigation of the outbreak.
The cases include 18 in Colorado and 8 scattered in California, Iowa, Michigan, South Dakota, Washington, and Wyoming, the Centers for Disease Control and Prevention (CDC) reported in the Jul 26 issue of Morbidity and Mortality Weekly Report. Seven patients were hospitalized in the outbreak, and five had hemolytic uremic syndrome, according to the report.
In the MMWR report and in a teleconference today, CDC officials said molecular subtyping played a key role in connecting the illnesses with one another and with the ConAgra ground beef. Pulsed-field gel electrophoresis (PFGE) was used to subtype the E coli isolates.
The analysis revealed the same pattern in isolates from all 18 Colorado patients, from ground beef that ConAgra recalled on Jun 30, and from ground beef from one patient's home. Investigation also traced the beef bought by the patient to the ConAgra plant and to the lot subject to the recall announced Jun 30. That lot consisted of 354,200 pounds of product produced May 31.
Among the eight patients outside Colorado, isolates from six had PFGE patterns that matched the outbreak pattern, and two patients were siblings of a PFGE-matched patient, the CDC report said.
The CDC said its PulseNet database includes molecular fingerprints of at least 9,800 microbial isolates. "The PFGE pattern of the human and meat isolates in this outbreak was novel in the PulseNet database, facilitating the detection and investigation of seemingly sporadic cases of E coli O157:H7 infection in Colorado and six other states and strengthening the association between the recalled beef products and human illness," the MMWR report states.
The ConAgra recall was expanded Jul 19 to include all ground beef produced at the Greeley plant between April 12 and Jun 29 and all beef trimmings produced there between Apr 29 and Jul 11, the CDC report notes. The report puts the total amount involved at 18.6 million pounds; the recall has been called the second largest on record.
So far all the outbreak cases have been tied to the meat subject to the initial Jun 30 recall, the CDC's Paul Mead, MD, said at today's teleconference. "No cases have been definitively linked to lots of meat from the expanded recall, but we can't rule out the possibility that there were cases," said Mead, who works in the National Center for Infectious Diseases' Division of Bacterial and Mycotic Diseases.
Mead said the CDC is continuing to investigate the outbreak. But in response to questions, he said the agency has no E coli isolates from the expanded recall. "The recovery of E coli from the other lots is based primarily on testing that the company did," he said.
The initial recall was "a bit unusual" in that it was unrelated to the epidemiologic investigation, Mead said. The recall was based on US Department of Agriculture product testing and was issued before any illnesses had been linked to the meat by molecular subtyping, he said.
The MMWR report makes it clear that the risk of E coli O157:H7 in beef is not likely to fade away any time soon. "The prevalence of E coli O157:H7 in feed lots can reach 63%-100%, particularly during the summer, under muddy conditions, or with feeding of barley," the report says. Further, "Consumers should be aware that microbiologic testing in meat processing plants cannot eliminate the risk for contamination of ground beef with E coli O157:H7 and other pathogens. To further reduce the risk for illness, consumers can buy ground beef that is precooked or treated with electron beams." The report also stresses the need for safe food-handling practices.
outbreak of Escherichia coli O157:H7 infections associated with
eating ground beef—United States, June-July 2002. MMWR 2002;51:29:637-9