Navigation

P2-44 Simultaneous Multi-pathogen Enrichment of Salmonella Species, E. coli O157:H7 and Listeria monocytogenes in Tomatoes

Monday, July 27, 2015
Exhibit Hall (Oregon Convention Center)
Kirsten Hirneisen , U.S. Food and Drug Administration , Irvine , CA
Chorng-Ming Cheng , U.S. Food and Drug Administration , Irvine , CA
Venugopal Sathyamoorthy , U.S. Food and Drug Administration , Laurel , MD
Atin Datta , U.S. Food and Drug Administration-CFSAN , Laurel , MD
Mei-Chi Siu , 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 including Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes, the most significant pathogens in FDA regulated food products.  As per the Bacteriological Analytical Manual (BAM), depending on the food matrix and target pathogen, different pre-enrichment broths are used for sample preparation prior to conventional culturing detection methods.  The use of multiple broths is labor intensive and a roadblock for multi-pathogen detection screening methods in foods or environmental swabs.  

Purpose: The objective of this study is to identify the best broth to use for simultaneous enrichment of Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in tomatoes followed by detection using multiplex qPCR. 

Methods: Salmonella Typhimurium, E. coli O157:H7, Listeria monocytogenes were co-inoculated into tomato homogenate in candidate enrichment broths (1:3 ratio), and incubated at 37°C.  Candidate broths included Universal Pre-Enrichment Broth (UPB), Tryptone Soy Broth (TSB), published research broth Salmonella, Staphylococcus and Listeria (SSL), and a FDA research broth (BMW).  After 24 h incubation, DNA was extracted for multiplex qPCR analysis.

Results: All three pathogens were able to grow simultaneously and be detected by multiplex qPCR after 24 h enrichment in all candidate broths without food matrices.  For enrichment in tomato homogenate, BMW broth showed the greatest potential for a universal enrichment broth as Ct values for Salmonella Typhimurium, E. coli O157:H7 and Listeria monocytogenes were 24.74 ± 4.3, 21.44 ± 0.18 and 29.43 ± 4.5 after 24 h, respectively. The Ct value for Listeria monocytogenes enrichment in BMW broth is significantly lower (P < 0.05), indicating greater growth, than the TSB (36.66 ± 1.12), UPB (35.02 ± 3.25) and SSL (33.05 ± 2.71). 

Significance: The results will improve current regulatory microbiological methods encompassing the recovery, enrichment, and detection of microbial pathogens from foods to provide a less labor intensive means to sample preparation and pathogen screening.

Back to: Poster Session 2 – Laboratory and Detection Methods; Meat, Poultry and Eggs; Dairy and Beverages; Food Law and Regulation; General Microbiology; Modeling and Risk Assessment
<< Previous Abstract | Next Abstract >>