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P3-201 Simultaneous Enrichment of Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes in Spices and Seafood

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Kirsten Hirneisen , U.S. Food and Drug Administration , Irvine , CA
Venugopal Sathyamoorthy , U.S. Food and Drug Administration - CFSAN , Laurel , MD
Atin Datta , U.S. Food and Drug Administration - CFSAN , Laurel , MD
Richelle Richter , U.S. Food and Drug Administration , Irvine , CA
Donna Williams-Hill , U.S. Food and Drug Administration , Irvine , CA
Introduction: Rapid detection of Salmonella spp., Escherichia coli, and Listeria monocytogenesin foods is important for the prevention of foodborne illnesses. In accordance with the FDA Bacteriological Analytical Manual (BAM), different enrichment broths are used for different target pathogens and food matrices. Multipathogen detection assays for foodborne pathogen detection are desired for increased efficiency and reduced cost to the laboratory. In order to achieve this, a broth that can enrich for multiple target pathogens simultaneously is essential.

Purpose: The objective was to identify the best enrichment broth to simultaneously enrich Salmonella Typhimurium, E. coli O157:H7 and L. monocytogenes in seafood and spices for a multiplex qPCR detection assay.

Methods: Salmonella Typhimurium, E. coli O157:H7 and L. monocytogeneswere co-inoculated in a 1:1:1 ratio into 25g of tuna or red pepper spice blended with 225g of a candidate enrichment broth. Candidate broths included BAM media such as Buffered Listeria Enrichment Broth (BLEB) and modified Buffered Peptone Water (mBPW), published research broths including SEL, an FDA Research Broth (BMW) and modifications of these broths. After 24h incubation at 35°C, multiplex qPCR was performed on DNA extracts for pathogen detection.

Results: All target pathogens were detected in tuna enrichment in all candidate broths. Variations in Ct values for Salmonella Typhimurium and E. coli O157:H7 between the candidate broths were significantly different (P <0.05). For example, E. coli O157:H7 Ct values ranged from 24.11±0.52 in mBPW+glucose to 36.1±6.25 in UPB (n=3). In red pepper, L. monocytogenes was not detected in BMW, Buffered BMW, mBPW and SSL broth enrichment. Salmonella Typhimurium, E. coli O157:H7, and L. monocytogeneshad Ct values of 29.26±2.09, 28.59±2.07 and 35.85±0.86, respectively, in red pepper mBPW+glucose enrichment.

Significance: The results will impact regulatory microbiological methods for the detection of multiple microbial target pathogens from foods and will provide a less labor intensive means for pathogen screening.

Back to: Poster Session 3 – Low-water Activity Foods, Packaging, Produce, Microbial Food Spoilage, Antimicrobials, Laboratory and Detection Methods, Water
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