Sep 21, 2006 (CIDRAP News) – Eleven more cases were identified today in a nationwide Escherichia coli O157:H7 outbreak related to fresh spinach, bringing the total to 157, the US Food and Drug Administration (FDA) reported.
David Acheson, MD, chief medical officer for the FDA's Center for Food Safety and Applied Nutrition, said at a news briefing that four more patients developed hemolytic uremic syndrome (HUS), a serious complication, bringing HUS cases to 27. Eighty-three people—more than half of those infected—were hospitalized in the outbreak. The death toll remained the same at 1 today.
Few new details emerged about investigations on nine farms in California's greater Salinas Valley that have been possibly linked to a fresh spinach sample that tested positive for E coli O157:H7. The results on the sample, collected from a bag of spinach from the home of a New Mexico patient, were announced yesterday. Acheson said about 10 or 15 more bags of spinach obtained from patients are being tested.
Officials are intensively discussing allowing spinach from unaffected regions to be sold again, he said. Authorities are working out what labeling should be used and are devising a message to ensure that consumers know the spinach that returns to stores is safe.
"A confused consumer is a consumer who's not confident about the safety of the food," Acheson said. He added that until those details are resolved, the advisory from the FDA remains the same: Don't eat fresh or raw spinach.
No new recalls were announced today. Three remain in effect: fresh spinach and products that contain fresh spinach produced or distributed by Natural Selections Foods, River Ranch, and RLB Food Distributors.
The FDA issued its fresh spinach alert on Sep 14, when the Centers for Disease Control and Prevention (CDC) announced that 50 patients in eight states had been diagnosed with E coli infections and that fresh or raw spinach was the food most of them had in common.
The CDC said this week that people who experience diarrhea after eating fresh spinach or salad blends containing fresh spinach should contact their healthcare provider and ask to have a stool sample tested for E coli O157:H7.
Concern about high HUS rate
At an E coli update for clinicians today, hosted by the CDC, Phillip Tarr, MD, director of the Division of Pediatric Gastroenterology and Nutrition at Washington University School of Medicine in St. Louis, said the high number of patients (27 of 157, or 17%) who developed HUS, particularly young adults, in the current outbreak was unexpected. Children usually have higher rates of HUS than adults. Tarr said the rate can be as high as 15% in children younger than 10 who have E coli infections.
At today's press briefing, Acheson reported that more than half of the HUS cases in this outbreak were in adults. He listed the following age distribution for the HUS patients: younger than 5 years, 7%; 5 to 19, 24%; 20 to 64, 55%, and 65 and older, 14%.
Earlier this week, Acheson said it was too early to reach conclusions about the virulence of the involved E coli strain, but he said the number of people who have been hospitalized seemed high. In a typical E coli outbreak, he said, 25% to 30% of patients require hospital treatment, compared with more than half of the patients identified so far in this episode.
Experts share diagnostic, management tips
Tarr said two notable symptoms of an E coli O157:H7 infection are watery diarrhea that often turns bloody and abdominal pain that is out of proportion to the diarrhea. He said adults usually have right-sided abdominal tenderness, whereas the tenderness in children is typically more generalized.
Patricia Griffin, MD, chief of the CDC's foodborne diseases epidemiology section, said patients with E coli infections have little or no fever. She advised clinicians who have patients with a suspected E coli infection to speak directly with labs before sending in stool samples. "Ask them if they look for O157 in every stool specimen; not all do," she said. "If they don't, ask them to add a routine enteric panel."
If the lab says it does test for O157:H7, clinicians should ask what test they use, Griffin said. The sorbitol-MacConkey agar test is preferred, but many labs instead use the more automated enzyme-linked immunosorbent assay (ELISA) test that screens for Shiga toxin, she said. Labs should hold on to positive samples for further testing and so that isolates can be sent to public health labs.
Both Griffin and Tarr said there is no evidence that antibiotics are helpful in treating patients who have E coli O157:H7 infections; in fact, they said antibiotics have been known to increase the production of Shiga toxin.
Hydration plays a key role in supportive care because of the profound coagulation activation seen in patients with these infections, Tarr said. Admitting patients to the hospital allows patients to receive intravenous isotonic saline solution to maintain kidney perfusion, enables physicians to monitor patients' platelet counts and other lab values, and prevents patients from spreading the infection to others, he said.
The platelet count is a useful barometer of the patient's risk of developing HUS and should be monitored daily, he said. "Once it starts to rise, the patient is usually out of the woods."
Sep 21 FDA press release
CIDRAP overview of pathogenic E coli