Joint USDA/FDA study using BAX® System microbe identification points to sources of grocery Listeria contamination

Pathogens can lurk at any point in grocer supply chain, long-term research finds


(31 August 2017) -- A three-year multistate Listeria bacteria contamination study conducted by the USDA, FDA and academic scientists found that pathogenic and benign forms of the bacteria can lurk in common groceries, and can occur at any point from delivery to final consumer purchase. Listeria monocytogenes is particularly challenging to food safety systems because it can survive at refrigeration temperatures.  Because ready to eat foods can easily transmit L. monocytogenes, the USDA and FDA conducted the major study to look at the prevalence of the pathogen in grocery stores and ready-to-eat facilities in stores and delis.

While the incident numbers in this study appear low, the results are significant because L. monocytogenes is a leading cause of death from foodborne illness, especially among vulnerable consumers such as children, the elderly, and the immunocompromised.

The USDA/FDA “Market Basket Survey,” conducted from 2010 to 2013 at groceries in California, Maryland, Connecticut and Georgia, used the Hygiena BAX® system, which utilizes polymerase chain reaction (PCR) technology to quickly and accurately detect microbes.

“We are pleased that this significant and comprehensive market basket survey selected the Hygiena BAX® Q7 system to accurately detect possible pathogens in groceries,” said Kyle Rhoden, BAX® system product manager at Hygiena. “We are proud to have pioneered the application of PCR technology to food safety many years ago and for our partnerships with government agencies and food companies in ensuring a safe food supply.”

The study found that of 27,389 samples from 16 food categories, the proportion containing the pathogen Listeria monocytogenes ranged from zero in soft-ripened and semisoft cheese to 1.07 percent for raw cut vegetables. For Listeria-like organisms (which may or may not be pathogenic), proportions of positive samples ranged from 0.79 percent for the same cheeses to 4.76 percent for fresh crab meat or sushi.

The study also found that L. monocytogenes contamination did not vary according to packaging location (either by manufacturer plant or at the grocery itself), or by the type of store (national versus local grocery brand), suggesting that contamination is possible at any point in processing, storing and selling food.

The survey did reveal some good news—samples of delicatessen meats, seafood, cheese, and salads showed a significantly lower rate of contamination incidence than the same study conducted by the same group 10 years ago.

The USDA has adopted the Hygiena BAX® system into the USDA’s Microbiology Laboratory Guidebook (MLG), a reference for microbiology methodologies used to protect the nation’s food supply, marking another level of acceptance of the BAX® System by the food safety industry. The system has been adopted by the agency for detecting L. monocytogenes, Campylobacter, Salmonella, Escherichia coli O157:H7, and non-O157 Shiga Toxin-Producing Escherichia coli (STEC).

The BAX® System is a breakthrough genetics-based screening method that detects target bacteria in raw ingredients, finished food products and environmental samples. The automated, easy-to-use system has been available since 2000, when the BAX® System revolutionized rapid food pathogen testing.  More than 20 years later, the trusted, tried and true technology of the BAX® System continues to be in use by governments, food companies and laboratories around the world.

The study, “Survey for Listeria monocytogenes in and on ready-to-eat foods from retail establishments in the United States (2010 through 2013): assessing potential changes of pathogen prevalence and levels in a decade” was published in the Journal of Food Protection (Volume 80, No. 6, pages 903-921). 




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