Labs Fail to Detect Cases of Bacterial Food Contamination

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Foodborne illnesses are a continuing problem in the U.S., but labs that are supposed to detect the presence of pathogens aren’t up to snuff, according to a new report.

The analysis, presented at the 113th General Meeting of the American Society for Microbiology, revealed worrisome gaps in the ability of food laboratories to detect or rule out the presence of common disease-causing bacteria such as E. coli, Salmonella, Listeria, and Campylobacter.

The study involved about 40,000 food laboratory proficiency tests conducted over the last 14 years and showed that food microbiology laboratories that are supposed to identify pathogens in food submit a disturbing number of false negative and false positive results. The data was compiled by the American Proficiency Institute (API), a private institute that monitors the accuracy of bacterial testing among labs that voluntarily submit to the review.

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API’s reviews occur up to three times a year and assess both the accuracy of the labs’ testing methods and the competency of their testing personnel. The tests determine, for example, whether the laboratory technicians can correctly identify pathogens that API officials add to food sample–or the absence of any bacteria.

Over the 14 year study period, API determined that on average, food laboratories had a false negative result rate (failing to identify the presence of a pathogen) of 9.1% for Campylobacter and 4.9% for Salmonella. On average, the labs reported false positive results (suggesting bacteria was in a food sample when it wasn’t) in 3.9% of cases for Salmonella and 2.5% for E. coli and L. monocytogenes.

Currently, API says that its testing is used in over 700 food laboratories in 43 countries. Widespread monitoring, its scientists say, could lead to more reliable and standardized monitoring for common food contaminants and ensure a safer food supply in the U.S., as well as lower rates of food related illness.

And addressing such foodborne disease remains an important public health concern; last month, the Centers for Disease Control (CDC) reported that about one in six people in the United States gets sick from eating contaminated food, and that rate has not declined in seven years.

Data from the FoodNet program, which tracks infections of nine of the most prevalent bacteria in food, including Listeria, salmonella, and E.coli, showed that although contamination rates have dropped since 1990, they have remained stagnant since 2006. In 2012, the FoodNet program identified 19,500 infections, including 4,500 hospitalizations and 68 deaths; these infection rates from the nine most common pathogens had not significantly changed since the previous analysis from 2006 to 2008.

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While improving the consistency of lab testing for pathogens that can contaminate food is an important step toward improving food safety, it won’t be enough. To lower rates of foodborne illnesses, the study authors, as well as public health experts hope that two draft proposals released by the U.S. Food and Drug Administration (FDA) in January will help to standardize methods of preventing bacterial exposure. The proposals are part of the Food Safety Modernization Act (FSMA) that President Obama signed in 2011.

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One, entitled Preventive Controls for Human Food calls for manufacturers selling food in the U.S., even if the products were grown abroad, to develop formal rules for preventing contamination of their products and to establish systems for correcting any problems that do occur.

The second proposal, Standards for Produce Safety concerns produce, and mandates stricter hygienic standards for workers handling produce as well as stronger requirements to maintain sanitary conditions during growing, harvesting, packing and storing processes. The rules also call for stricter monitoring of animals that can enter crop fields.

The rules are still open to public comment until September 16. You can read more, and comment on the proposals, here.

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