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P1-37 Analysis of Salmonella spp. Enrichment for Foodborne Pathogen Detection

Monday, August 4, 2014
Exhibit Hall D (Indiana Convention Center)
Kirsten Hirneisen, U.S. Food and Drug Administration, Irvine, CA
Chorng-Ming Cheng, U.S. Food and Drug Administration, Irvine, CA
Donna Williams-Hill, U.S. Food and Drug Administration, Irvine, CA
Introduction: For successful prevention of foodborne illness, rapid and reliable methods are needed for pathogen detection. Depending on the food matrix, varying pre-enrichment broths are used by FDA field labs as outlined in the Bacteriological Analytical Manual (BAM) for individual pathogen detection.  The use of multiple pre-enrichment broths is labor intensive and a roadblock for efforts in multi-pathogen detection screening methods in foods or environmental swabs.  

Purpose: This study aims to characterize growth of Salmonella spp. in candidate enrichment broths in an effort to identify a universal enrichment broth capable of supporting growth of multiple Salmonella serovars. 

Methods: Candidate broths included current BAM broths, a FDA research broth (BMW) and modifications of these broths.  Salmonella spp. (Agona, Bareilly, Braenderup, Brandenberg, Enteritidis, Javiana, Montevideo, Newport, Poona, Saintpaul, Tennessee and Typhimurium) were individually inoculated into candidate enrichment broths to achieve a final concentration of approximately 5 CFU/ml.  Growth was analyzed in an automatic growth curve analyzer at 37°C for 24h with OD600nm readings taken every 20 minutes.  After 24h of incubation, samples were plated on TSA and XLD.  Lag times and maximum growth rates were calculated from OD600nmusing DMFit. 

Results: After 24h, all Salmonella spp. growth was > 9 log CFU/ml in all broths but growth rates varied by serovar and broth. BMW and UBP broths had the lowest lag times, 4.16 ± 0.93h for Salmonella Saint Paul in BMW and 3.69 ± 0.14h for Salmonella Braenderup in UPB, indicating the fastest growth.  Salmonella Typhimurium had the highest lag times for all broths, ranging from 7.65 ± 0.43h to 11.83 ± 0.05h. 

Significance: Identification of the vital constituents for Salmonella growth in enrichment broths will ultimately be used for formulation of a universal enrichment broth enhancing detection of multiple Salmonella spp. in food and environmental samples.

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