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United States Department of Agriculture

Agricultural Research Service

2007 Annual Report

1a.Objectives (from AD-416)
1) Develop phylogenetic and phenotypic markers for E. coli O157:H7, non-O157 STEC/EHEC, and Salmonella spp. based on genomic and proteomic strain comparisons, expression analysis, and multi-drug resistance profiles for use in molecular strain typing, intervention method development, and design of multiple pathogen detection schemes. 2) Determine prevalence of unrecognized foodborne pathogens such as Shiga toxigenic E. coli on fresh imported beef to be used for ground beef and establish necessary profiling to insure imported beef products meet the same levels of safety as domestic products. 3) Identify sources of spoilage bacteria and pathogen contamination during beef transport/processing/slaughter (i.e., transport vehicles, lairage pens, air, hides, feces) and develop novel antimicrobial intervention strategies. 4) Determine the microbiological safety of lamb processed in the United States and determine the efficacy of currently used intervention technologies during various stages of lamb processing.

1b.Approach (from AD-416)
Strain specific markers will be identified and will be used for tracking, typing, virulence, and detection assays. Identification of the strain specific markers will lead to a more complete understanding of bovine-related foodborne pathogen ecology in which the pathogens of concern are not the same as those of the United States. The microbial profile of ground beef imported from countries will be determined in order to establish the most effective testing guidelines. Employing traditional methodologies as well as implementing new strategies developed in Objective 1, researchers in this unit will continue longstanding efforts in tracking pathogen contamination. To better understand the contribution of feedlot settings, livestock transport, and husbandry equipment to pathogen contamination, focus will be placed on identifying surface and airborne bacterial populations associated with transport vehicles, lairage pens, and slaughter facilities. Efforts will continue in evaluating pathogen carriage on hides and in feces. New efforts will be initiated to identify sources of other pathogen and spoilage bacterial contaminants including, but not limited to, non-O157 Shiga toxin-producing E. coli (STEC), Salmonella spp. and Clostridium spp. As new sources of pathogen contamination are identified, research will be undertaken to develop and evaluate novel antimicrobial strategies. Projects will be performed to determine the prevalence of foodborne pathogens (i.e., Escherichia coli O157:H7, Salmonella, and non-O157 STEC) and the level of aerobic bacteria on lamb carcasses processed in the United States. Understanding sources of carcass contamination will identify critical control points where antimicrobial intervention technologies need to be used to reduce or eliminate carcass contamination and to ensure wholesome meat. These results will be useful for the lamb industry and the USDA Food Safety and Inspection Service (FSIS).

Transportation and Lairage Environment Effects on Prevalence and Levels of Escherichia coli O157:H7 on Hides and Carcasses of Beef Cattle at Processing - Hide has been established as the main source of carcass contamination during processing, therefore, it is crucial to minimize the amount of Escherichia coli O157:H7 on cattle hides prior to slaughter. There are several potential sources of E. coli O157:H7 encountered in the transportation to and lairage environment (holding pens, alley ways, etc.) at beef processing facilities that could increase the prevalence and levels of E. coli O157:H7 on the hides of cattle. Scientists in Clay Center, NE, conducted a study to determine the extent to which E. coli O157:H7 is transferred to cattle hides and, subsequently, to carcasses during transport to and while in holding at beef processing plants. The results of this study demonstrate that transport to and lairage at processing plants leads to increased prevalence and levels of E. coli O157:H7 contamination on hides and carcasses. A major implication of this finding is that pre-harvest intervention effects would be negated by pathogen transfer in the lairage environment. This accomplishment addresses National Program 108 Problem Statement 1.2.3: Production and Processing Ecology.

Effects of a Minimal Hide Wash Cabinet on the Levels and Prevalence of E. coli O157:H7 and Salmonella on the Hides of Beef Cattle at Slaughter - Harborage of Escherichia coli O157:H7 and Salmonella on animal hides at slaughter is the main source of beef carcass contamination during processing. Given this finding, interventions have been designed and implemented to target the hides of cattle following entry into beef processing plants. Previous interventions targeting hides have not been suitable for all beef processing plants to implement due to cost and space restrictions. USMARC scientists evaluated a hide wash cabinet design that was smaller and more economical and, therefore, might be more amenable to widespread use in the beef processing industry. This study showed large reductions in E. coli O157:H7 and Salmonella levels after hide washing in the test cabinet. Based on these results, the hide wash cabinet described in this study was effective and should provide beef processors, especially small and medium-sized processing plants, with an affordable hide wash intervention strategy. This accomplishment addresses National Program 108 Problem Statement 1.2.4: Processing Intervention Strategies.

Microbiological Characterization of Imported and Domestic Boneless Beef Trim Used for Ground Beef - The United States imports lean boneless beef trim from Australia (AUS), New Zealand (NZL), and Uruguay (URY) to meet demand for ground beef production. The reported incidence of, and the bacteria responsible for, foodborne disease differ between these countries and the United States. USMARC scientists determined if current United States microbiological profiling adequately addresses the potential differences in the foreign and domestic beef trim, by comparing the hygienic status of imported and domestic (USA) beef trim by enumeration of aerobic bacteria, Enterobacteriaceae, coliforms, Escherichia coli and Staphylococcus aureus. We also compared the prevalence of pathogens between imported and domestic samples by screening for the presence of Salmonella, Campylobacter spp., Listeria spp., and non-O157 Shiga toxin-producing Escherichia coli (STEC). The results of this work showed that the current pathogen monitoring procedures in the United States do not need to be changed for imported beef trim. This accomplishment addresses National Program 108 Problem Statement 1.2.7: Risk Assessment.

Rapid Enrichment Strategy for Isolation of Listeria from Bovine Hide, Carcass, and Meat Samples - In keeping with the need to continually improve the food safety of beef products, USMARC scientists developed and validated a novel rapid method for detection of Listeria monocytogenes. An enrichment medium, Tryptic soy broth (TSB), was tested in place of the traditional enrichment media University of Vermont modification medium (UVM) to allow for resuscitation of injured bacterial cells. No difference between TSB and UVM was observed during primary enrichment for the isolation of Listeria spp. The significance of this work is that using TSB as a primary enrichment medium for the isolation of Listeria results in a time savings and a cost savings, and the number of manipulations required for each sample is decreased. Additionally, this work provides a method development that may enable the end user to screen food samples for Listeria spp. using a high-throughput method. This accomplishment addresses National Program 108 Problem Statement 1.2.1: Detection and Validation.

Microbiological Characterization of Lamb Carcasses at Commercial Processing Plants in the United States - Although the United States (U.S.) produces 203 million pounds of domestic lamb and mutton each year, thorough studies of the microbiological safety during lamb processing are lacking. To address this missing information, USMARC scientists collected samples from multiple large commercial lamb processing plants to determine levels of generic bacteria and the prevalences of Escherichia coli O157:H7, non-O157 Shiga toxin-producing E. coli (STEC), and Salmonella. The results of this study establish a baseline for microbiological quality and prevalences of Salmonella, E. coli O157:H7, and STEC in U.S. lamb processing plants as well as provide information as to the efficacy of various antimicrobial interventions in reducing bacterial pathogens on lamb carcasses. This accomplishment addresses National Program 108 Problem Statement 1.2.3: Production and Processing Ecology and Problem Statement 1.2.4: Processing Intervention Strategies.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of non-peer reviewed presentations and proceedings2
Number of newspaper articles and other presentations for non-science audiences3

Review Publications
Nou, X., Arthur, T.M., Bosilevac, J.M., Harhay, D.M., Guerini, M.N., Kalchayanand, N., Koohmaraie, M. 2006. Improvement of immunomagnetic separation for Escherichia coli O157:H7 detection by the pickpen magnetic particle separation device. Journal of Food Protection 69:2870-2874.

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.

Bosilevac, J.M., Guerini, M.N., Harhay, D.M., Arthur, T.M., Koohmaraie, M. 2007. Microbiological characterization of imported and domestic boneless beef trim used for ground beef. Journal of Food Protection 70(2):440-449.

Arthur, T.M., Bosilevac, J.M., Harhay, D.M., Guerini, M.N., Kalchayanand, N., Shackelford, S.D., Wheeler, T.L., Koohmaraie, M. 2007. Transportation and lairage environment effects on prevalence, numbers, and diversity of Escherichia coli O157:H7 on hides and carcasses of beef cattle at processing. Journal of Food Protection 70(2):280-286.

Arthur, T.M., Bosilevac, J.M., Brichta-Harhay, D.M., Kalchayanand, N., Shackelford, S.D., Wheeler, T.L., Koohmaraie, M. 2007. Effects of a Minimal Hide Wash Cabinet on the Levels and Prevalence of Escherichia coli O157:H7 and Salmonella on the Hides of Beef Cattle at Slaughter. Journal of Food Protection 70:1076-1079.

Arthur, T.M., Bosilevac, J.M., Nou, X., Shackelford, S.D., Wheeler, T.L., Koohmaraie, M. 2007. Comparison of the molecular genotypes of Escherichia coli O157:H7 from the hides of beef cattle in different regions of North America. Journal of Food Protection. 70(7):1622-1626.

Last Modified: 11/29/2015
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