Evaluation of Universal Pre-Enrichment Broth for Isolation ofSalmonellaspp.,Escherichia coliO157:H7, andListeria monocytogenesfrom Dairy Farm Environmental Samples

Abstract

Use of universal pre-enrichment broth (UPB) as a primary enrichment medium for detection of Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes from dairy farm environmental samples was evaluated. There were no differences in bacterial growth between UPB and selective primary enrichment broths for each pathogen inoculated individually or in combination at 10(1) and 10(2) colony forming units/mL. In addition, no differences were observed when UPB and selective primary enrichment broths were compared for detection efficiency of pathogens in artificially contaminated raw milk and fecal samples. Listeria enrichment broth (LEB) was compared with UPB to support growth of L. monocytogenes from naturally contaminated environmental samples. Listeria monocytogenes was isolated from seven of 30 samples enriched in UPB and six of 30 samples enriched in LEB. Dairy farm environmental samples were examined for recovery of the three pathogens using UPB. Subsequent isolation was achieved using selective secondary enrichment of each pathogen. Listeria monocytogenes, Salmonella spp., and E. coli O157:H7 were isolated in 13.4% (30 of 224), 8.9% (20 of 224), and 2.2% (five of 224) of samples, respectively. Isolation rates of the three pathogens were somewhat higher than in previous reports. Overall, UPB supported growth of test pathogens to detectable levels within 24 h. Our results demonstrate that UPB has potential for routine use in isolation of foodborne pathogens from diverse environmental samples.