Tomatoes confirmed as source of Salmonella outbreak

Nov 3, 2006 (CIDRAP News) – Federal officials said today they have zeroed in on restaurant tomatoes as the cause of a recent nationwide Salmonella outbreak.

At a press conference, Christopher Braden, MD, chief of outbreak response and surveillance in the foodborne disease branch of the Centers for Disease Control and Prevention (CDC), said 183 Americans from 21 states were sickened in the outbreak. Two Canadians also fell ill. Twenty two (12%) patients were hospitalized, which Braden said was typical for a Salmonella enterica serotype Typhimurium outbreak.

The organism typically causes fever and nonbloody diarrhea that resolves in a week.

The CDC detected the outbreak 2 weeks ago through PulseNet, an electronic network for sharing molecular fingerprinting (pulsed-field gel electrophoresis) data. At the same time, states were noticing clusters of patients who had the same strain and genetic fingerprint. The CDC said cases in the outbreak have been reported since Sep 1. Most of the states affected are in the eastern half of the nation.

The CDC and the Food and Drug Administration (FDA) now consider the outbreak over, and they don't believe the public is at risk. David Acheson, MD, chief medical officer for the FDA's Center for Food Safety and Applied Nutrition, said all of the tomatoes associated with the outbreak have been destroyed, thrown out, or eaten by now. "So there's no need for a warning for consumers," he said.

A case-control study, which involved interviews with sick and well people about their recent food histories, helped the CDC narrow the cause to restaurant tomatoes, Braden said, adding that the contaminated products were not linked to a specific chain or type of restaurant or a specific growing region.

Acheson said the next step is a trace-back investigation to determine where and when the restaurants purchased the tomatoes and to try to identify the involved production facilities and farms. "It may be a couple weeks before we have a common denominator," he said.

Several disease outbreaks involving contaminated tomatoes have occurred in the past 7 or 8 years, Acheson said. The FDA met with Florida and Virginia tomato producers in 2004 and 2005 to discuss food safety problems. He said the next such industry forum, cosponsored by the University of Florida and the Florida Tomato Exchange, will be held in Orlando at the end of November.

The Salmonella outbreak is the second major produce-contamination event in recent months. In late August and September, fresh spinach contaminated with Escherichia coli O157:H7 sickened 204 people in 26 states. Three deaths were linked to the outbreak.

Acheson said he's not sure if produce contamination is increasing or if more outbreak reports are due to better recognition of illness or higher consumption of fresh produce. Braden said another factor may be the increased centralization of the fresh produce industry over the past several decades. Larger food-processing operations, he said, may face a greater risk of cross-contamination than smaller, less centralized operations.

See also:

CIDRAP overview of salmonellosis
http://www.cidrap.umn.edu/cidrap/content/fs/food-disease/causes/salmoview.html

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