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United States Department of Agriculture

Agricultural Research Service

2008 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).

3.Progress Report
We evaluated the efficacy of a novel antimicrobial agent in decontamination of beef tissue. 1, 3-Dibromo-5, 5-Dimethylhydantoin (DBDMH), commercially called Bromitize, and hot water spray treatments were evaluated for efficacy in decontamination of pathogenic bacteria attached to beef carcass surfaces represented by flank tissue sections and beef hearts. Following Bromitize or hot water spray treatments, bacterial populations were counted immediately and after storage for 48 h at 4°C. This study demonstrated Bromitize spray washing could be effective as an antimicrobial intervention for red meat carcasses and variety meats. Much of the research to date on reducing E. coli O157:H7 from the food supply has been focused on the post-harvest side of the production chain. Pre-harvest interventions do not share the same wealth of techniques that have been proven effective against these bacterial pathogens. Direct Fed Microbials (DFM) have been identified as potential pre-harvest interventions for the reduction of foodborne bacterial pathogens. We determined the effect on E. coli O157:H7 and Salmonella prevalence and load from feeding a DFM to feedlot cattle. Hide and fecal samples obtained from 526 heifers were followed over an 84-day finishing period. The data from this experiment leads to the conclusion the DFM tested would not be an effective pre-harvest intervention against E. coli O157:H7. There were not sufficient observations of Salmonella to enable substantive conclusions to be made. Salmonella, and Salmonella resistant to multiple antibiotics (MDR-Salmonella), have been observed in the meat production environments, but solid data identifying their source is lacking. We conducted research projects to.
1)determine if lymph nodes are a source of Salmonella that could potentially contaminate ground beef products;.
2)determine if MDR Salmonella can be attributed to cattle from a particular production environment such as cull beef cows, dairies, or feed lots; and.
3)enumerate Salmonella throughout the commercial pork harvesting process. These projects will aid our understanding of the ecology of Salmonella in processing environments. There is ample data on the prevalence and levels of E. coli O157:H7 and Salmonella found during the different steps of harvest at large U.S. beef processing plants. However, a significant portion of the U.S. beef supply passes through small processing plants, for which little data is available. For this study "small processing plants" was defined as processors who harvest less than 1,000 cattle a day. More data on contamination rates was needed to assist in developing technology to reduce the risk of pathogen contamination of carcasses and help determine the best processes to put into place to reduce hide levels of pathogens. It is well known higher levels of pathogens on hides positively correlate to greater risk of pathogen on carcasses. USMARC scientists determined the prevalence and enumerated the levels of E. coli O157:H7 and Salmonella on hides and pre-evisceration carcasses of cattle processed through smaller plants. The processors were able to rapidly improve pathogen control by changing hide removal steps.

1. Lairage Contamination Intervention. ARS scientists in Clay Center, NE, utilized molecular tracking to determine that the transfer of bacteria onto cattle hides that occurs in the lairage environments (holding pens, alleyways, etc.) of U.S. beef processing plants account for a larger proportion of the hide and carcass contamination than does the initial bacterial population found on the cattle exiting the feedlot. These results suggest pre-harvest interventions must be implemented by everyone to be effective. This work also identified that hide wash cabinets effectively remove this contamination before it can be transferred to the carcass. This accomplishment addresses NP 108 Action Plan Component 1.2 Problem Statement 1.2.4: Processing Intervention Strategies.

2. Intervention Effectiveness on Multidrug Resistant Salmonella. Several strains of Salmonella have been identified as being resistant to multiple antibiotics. It was not known if strains possessing multidrug resistance properties also have the ability to resist the killing effects of the antimicrobial interventions used in beef processing. ARS scientists in Clay Center, NE, demonstrated that multidrug resistant Salmonella are reduced at least as effectively as Escherichia coli O157:H7 and susceptible Salmonella when treated with antimicrobial interventions currently in use at most U.S. beef processing plants. This accomplishment addresses NP 108 Action Plan Component 1.2 Problem Statement 1.2.4: Processing Intervention Strategies.

3. Intervention Effectiveness on Human Disease-Associated E. coli O157:H7. Recent studies have determined that within the E. coli O157:H7 population, variation exists with regard to the ability to cause human disease. Specific genetic markers have been identified in E. coli O157:H7 strains that are associated with higher incidences of human disease. ARS scientists in Clay Center, NE, determined that there was no difference in the abilities of these two groups to survive antimicrobial interventions. These results indicate that the likelihood to cause human illness by E. coli O157:H7 does not influence the antimicrobial efficacy of the interventions utilized by the modern beef processing plants. This accomplishment addresses NP 108 Action Plan Component 1.2 Problem Statement 1.2.4: Processing Intervention Strategies.

4. Antimicrobial Interventions for Beef Heads. Variety meats, including head and cheek meats, hold a significant value in the retail market. However, during processing, heads are not always subjected to the same antimicrobial interventions as carcasses, increasing their food safety risk. ARS scientists in Clay Center, NE, examined the impact of several antimicrobial interventions in removing E. coli O157:H7 from beef heads. Based on the results of this study, several treatments were identified as effective in inactivating E. coli O157:H7 on bovine head and cheek meat. This accomplishment addresses NP 108 Action Plan Component 1.2 Problem Statement 1.2.4: Processing Intervention Strategies.

5. Salmonella in Bovine Lymph Nodes. A potential source of pathogenic bacteria in ground beef is the lymphatic system, specifically the lymph nodes. There are several reports of bacteria isolated from the lymph nodes of cattle at slaughter; however, most of the studies have dealt with mesenteric lymph nodes that are not normally incorporated into ground beef. ARS scientists in Clay Center, NE, determined the prevalence and multidrug-resistance status of Salmonella in bovine lymph nodes associated with lean and fat trimmings that might be utilized in ground beef production. Salmonella prevalence in the lymph node samples was low with an overall prevalence of 1.6%. Multidrug resistant Salmonella were detected in 0.03% of the samples. This accomplishment addresses NP 108 Action Plan Component 1.2 Problem Statement 1.2.3: Production and Processing Ecology.

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 Audiences1

Review Publications
Harhay, D.M., Arthur, T.M., Bosilevac, J.M., Guerini, M.N., Kalchayanand, N., Koohmaraie, M. 2007. Enumeration of Salmonella and Escherichia coli O157:H7 in ground beef, cattle carcass, hide and faecal samples using direct plating methods. Journal of Applied Microbiology 103(5):1657-1668.

Guerini, M.N., Harhay, D.M., Shackelford, S.D., Arthur, T.M., Bosilevac, J.M., Kalchayanand, N., Wheeler, T.L., Koohmaraie, M. 2007. Listeria prevalence and Listeria monocytogenes serovar diversity at cull cow and bull processing plants in the United States. Journal of Food Protection. 70(11):2578-2582.

Kalchayanand, N., Arthur, T.M., Bosilevac, J.M., Harhay, D.M., Guerini, M.N., Shackelford, S.D., Wheeler, T.L., Koohmaraie, M. 2007. Microbiological characterization of lamb carcasses at commercial processing plants in the United States. Journal of Food Protection 70(8):1811-1819.

Kalchayanand, N., Arthur, T.M., Bosilevac, J.M., Brichta-Harhay, D.M., Guerini, M.N., Wheeler, T.L., Koohmaraie, M. 2008. Evaluation of various antimicrobial interventions for the reduction of Escherichia coli O157:H7 on bovine heads during processing. Journal of Food Protection 71(3):621-624.

Harhay, D.M., Arthur, T.M., Koohmaraie, M. 2008. Enumeration of Salmonella from poultry carcass rinses via direct plating methods. Letters in Applied Microbiology 46(2):186-191.

Last Modified: 11/27/2015
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