PREVALENCE OF ESCHERICHIA COLI O157:H7, LISTERIA MONOCYTOGENES, AND SALMONELLA IN TWO GEOGRAPHICALLY DISTANT COMMERCIAL BEEF PROCESSING PLANTS IN THE UNITED STATES

Authors: Rivera Betancourt, Mildred; Shackelford, Steven; Arthur, Terrance; WESTMORELAND, KURT - SILLIKER LABS; BELLINGER, GINA - FOOD SAFETY NET SERVICES; ROSSMAN, MICHELLE - NAT'L CATTLEMEN'S BEEF; REAGAN, JAMES - NAT'L CATTLEMEN'S BEEF; Koohmaraie, Mohammad

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2003
Publication Date: 1/20/2004
Citation: Rivera Betancourt, M., Shackelford, S.D., Arthur, T.M., Westmoreland, K.E., Bellinger, G., Rossman, M., Reagan, J.O., Koohmaraie, M. 2004. Prevalence of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella in two geographically distant commercial beef processing plants in the United States. Journal of Food Protection. 67:295-302.

Interpretive Summary: Escherichia coli O157:H7, Listeria spp., L. monocytogenes, and Salmonella spp. are associated with food-borne illness and death, and have been linked to contamination of meat and meat products. Sources of these pathogens on carcasses during slaughter are multiple and are associated with the animal, processing practices, slaughter plant facilities, and employees. During the slaughter process, pathogenic bacteria can be transferred to the beef carcass and, thus, enter the food supply. We examined the prevalence of the above-mentioned pathogens at two commercial beef processing plants (north and south) in the United States. Samples were taken from the plant's environment (fifteen sites within each plant before operation, anytime during operation, and late in operation) as well as from animal hides and carcasses (pre-evisceration and post-intervention) during a five-month period. Samples were analyzed for the presence of the pathogens, and prevalence on hide, carcass, and plant environment was established according to geographical location and seasonality. The results in this study established that hides and fence panels in the holding pens are sources of contamination in the preslaughter environment and can be used to determine the contamination pattern of the carcasses. For instance, in the southern plant, Salmonella spp. and E. coli O157:H7 were predominant in hides and fence panels whereas Listeria spp. and L. monocytogenes were predominant in the northern plant, and similar patterns of the incidence of the specific pathogens were observed on carcasses and in-plant environment. Furthermore, seasonality and geographical location are also factors that can be used as predictors of these pathogens, since the prevalence of E. coli O157:H7 and Salmonella spp. on hides was sustained for a longer period of time in the southern plant (May, July, August, and October). The present study also revealed that processing equipment, contact surfaces (conveyor belts), and plant personnel could be critical points of meat contamination by these pathogens at anytime during processing. The environmental sites identified as positive for these pathogens were in the slaughter floor, fabrication floor, and locker room. Differences in the prevalence of specific pathogens from the eleven environmental sites tested were observed among the plants. For instance, in the northern plant, Listeria spp, L. monocytogenes, and Salmonella spp. were detected on fabrication floor conveyor belts late during the production day, whereas Salmonella spp. was only detected in this site in the southern plant. In addition, in the northern plant, E. coli O157:H7, Listeria spp., and L. monocytogenes were detected in pre-operational fabrication floor conveyor belt samples. Overall, the results showed that there is a seasonal and geographical difference in the prevalence of this pathogen between the northern and southern plants. Moreover, this is the first report that shows prevalence of Listeria spp. and L. monocytogenes on cattle hide, fence panels in the holding pens, and pre-evisceration carcasses, in the United States. The prevalence pattern of the pathogens tested was similar before slaughter and in each plant's environment.

Technical Abstract: For two fed-beef slaughter and processing plants, one located in the southern United States and one located in the northern United States, prevalence of E. coli O157:H7, Salmonella spp., Listeria spp., and Listeria monocytogenes was determined for hide, carcass, and environmental samples. The prevalence of E. coli O157:H7 (68.1 vs 55.9%) and Salmonella spp. (91.8 vs 50.3%) was higher (P < 0.05) and the prevalence of Listeria spp. (37.7 vs 75.5%) and L. monocytogenes (0.8 vs 18.7%) was lower (P < 0.05) for the hides of cattle slaughtered at the southern vs the northern plant. Similarly, the prevalence of Salmonella spp. (52.0 vs 25.3%) was higher (P < 0.05) and the prevalence of Listeria spp. (12.0 vs 40.0%) and L. monocytogenes (1.3 vs 14.7%) was lower (P < 0.05) for the fence panels of the holding pens of the southern vs the northern plant. The prevalence of E. coli O157:H7 (3.1% vs 10.9%), Listeria spp. (4.5 vs 14.6%), and L. monocytogenes (0.0 vs 1.1%) was lower (P < 0.05) for pre-evisceration carcasses sampled at the southern vs the northern plant. Salmonella spp. (both plants), Listeria spp. (northern plant), and L. monocytogenes (northern plant) were detected on fabrication floor conveyor belts (product contact surfaces) late during the production day. For the northern plant, 21 of 148 (14.2%) late-operational fabrication floor conveyor belt samples were L. monocytogenes-positive. For the northern plant, E. coli O157:H7, Listeria spp., and L. monocytogenes were detected in pre-operational fabrication floor conveyor belt samples. Overall results suggest that there are regional differences in the prevalence of pathogens on the hides of cattle presented for slaughter at fed-beef packing plants and that these differences may affect the prevalence of these pathogens on carcasses and in the packing plant environment.