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United States Department of Agriculture

Agricultural Research Service

Title: Rapid Enrichment Strategy for Isolation of Listeria from Bovine Hide, Carcass, and Meat Samples

Authors
item Guerini, Michael
item Bosilevac, Joseph
item Koohmaraie, Mohammad

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 29, 2006
Publication Date: November 1, 2007
Citation: Guerini, M.N., Bosilevac, J.M., Koohmaraie, M. 2007. Rapid enrichment strategy for isolation of Listeria from bovine hide, carcass, and meat samples. Journal of Food Protection 70(1):53-57.

Interpretive Summary: Since the outbreak of foodborne illness linked to Escherichia coli O157:H7 bacteria in ground beef in the early 1980s, the beef processing industry has focused on increasing the safety of beef products by implementing procedures for surveying live cattle, carcasses, and beef products for bacterial pathogens. Effective methods are in place for screening cattle and beef products for the presence of E. coli O157:H7 contamination and recent work has established the acceptability of these methods for surveillance of Salmonella. In keeping with the need to continually improve the food safety of beef products, new work investigating pathogen prevalence is now including surveillance for Listeria monocytogenes. L. monocytogenes is the causative agent of listeriosis and the consequences from contracting listeriosis can be severe, especially in immunocompromised individuals, with mortality rates approaching 30% in people who become infected. This pathogen is present throughout the environment and has been isolated from numerous animal sources including cattle. Tryptic soy broth (TSB) has been documented as a robust non-selective medium for the enrichment of both E. coli and Salmonella species from bovine hide, carcass, and meat samples. The University of Vermont modification medium (UVM) is most often used as the primary enrichment medium for surveillance of Listeria species. In this study, TSB was tested for use in the detection of Listeria species compared to the more commonly used UVM medium. Results demonstrate that TSB detects the same prevalence level of Listeria and, more importantly, Listeria monocytogenes when compared to the UVM medium. However, use of TSB reduces both the cost and time requirements of the detection method. Additional modifications of the method provide for high-throughput sample processing. The new detection protocol for Listeria provides a high-throughput sample processing methodology that saves time and reduces the cost.

Technical Abstract: Since the outbreak of foodborne illness linked to Escherichia coli O157:H7 bacteria in ground beef in the early 1980s, the beef processing industry has focused on increasing the safety of beef products by implementing procedures for surveying live cattle, carcasses, and beef products for bacterial pathogens. Effective methods are in place for screening cattle and beef products for the presence of E. coli O157:H7 contamination in beef and recent work has established the acceptability of these methods for surveillance of Salmonella. In keeping with the need to continually improve the food safety of beef products, new work investigating pathogen prevalence is now including surveillance for Listeria monocytogenes. Tryptic soy broth (TSB) has been documented as a robust non selective medium for the enrichment of both E. coli and Salmonella species from bovine hide, carcass, and meat samples. The University of Vermont modification medium (UVM) is most often used as the primary enrichment medium for surveillance of Listeria species. In this study, samples from bovine hides (n = 50), pre evisceration carcasses (n = 50), and beef trim (n = 193) were used to evaluate TSB as a primary enrichment medium for the isolation of Listeria species including L. monocytogenes. No significant difference (P > 0.05) between TSB and UVM was observed when they were used as the primary enrichment for the isolation of Listeria spp. from any of the three sample types. Furthermore, the standard secondary enrichment ratio for Fraser broth used for Listeria recovery can be modified to accommodate a high-throughput method for processing multiple samples.

Last Modified: 11/27/2014