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Title: Enumeration of Escherichia coli cells on chicken carcasses as a potential measure of microbial process control in a random selection of slaughter establishments in the United States

Author
item ALTEKRUSE, SEAN - USDA-FSIS
item Berrang, Mark
item MARKS, HARRY - Food Safety Inspection Service (FSIS)
item PATEL, BHARAT - Food Safety Inspection Service (FSIS)
item SHAW, JR, WILLIAM - Food Safety Inspection Service (FSIS)
item SAINI, PARMESH - Food Safety Inspection Service (FSIS)
item BENNETT, PATRICIA - Food Safety Inspection Service (FSIS)
item Bailey, Joseph

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2009
Publication Date: 6/1/2009
Citation: Altekruse, S., Berrang, M.E., Marks, H., Patel, B., Shaw, Jr, W.K., Saini, P., Bennett, P.A., Bailey, J.S. 2009. Enumeration of Escherichia coli cells on chicken carcasses as a potential measure of microbial process control in a random selection of slaughter establishments in the United States. Applied and Environmental Microbiology. 75(11):3522-3527.

Interpretive Summary: Broiler processing is very effective at lowering the presence and numbers of bacteria on carcasses including human pathogens such as Campylobacter and Salmonella. However, low numbers of these organisms may still be found on processed carcasses. In order to assure that broiler processing is under control, the USDA-Food Safety Inspection Service tests carcasses for presence of Salmonella and numbers of E. coli. Concern also exists about the presence of Campylobacter on processed carcasses. Tests to detect the presence and numbers of Salmonella and Campylobacter are time consuming and expensive while tests for E. coli is relatively fast, easy and inexpensive. There is interest in the possibility of using E. coli numbers on broiler carcasses as an indication of process control. The hypothesis was that if processing is adequate to lower numbers of E. coli, which is almost always present on carcasses, than the numbers of other bacteria should be similarly affected. This study was conducted in 20 U.S. commercial broiler processing plants to measure the numbers of E. coli and Campylobacter and the presence of Salmonella on carcasses at an early stage and again at a late stage of processing. In four replicate sampling trips, a total of 800 carcasses were examined at two sites in order to measure the decrease in bacterial contamination due to processing. Overall, numbers of E. coli and Campylobacter and the prevalence of Salmonella were reduced by processing. Campylobacter was generally reduced more than E. coli. Although not an accurate predictor of Salmonella presence, statistical analysis shows that measurement of E. coli numbers may be useful as a means to confirm proper broiler processing to lower bacterial contamination of carcasses.

Technical Abstract: The purpose of this study was to evaluate whether the measurement of Escherichia coli levels at two points during the chicken slaughter process has utility as a measure of quality control. A one year long survey was conducted during 2004 and 2005 in 20 randomly selected United States chicken slaughter establishments with more than 500 employees. In each establishment, every three months, ten 100-ml carcass rinses were collected from a flock at early (rehang) and late (post-chill) processing locations. Escherichia coli and Campylobacter levels were measured by direct plating. Salmonella incidence was determined by enrichment and plating of PCR positive rinses. Positive correlations were seen between log 10 E coli and Campylobacter levels at several data aggregation levels. Reductions in Campylobacter levels between rehang and post-chill were generally greater than those for E. coli. In these plants, the post-chill mean log 10 E. coli level was less than 1.0 and the within 10 carcass-sample set standard deviation was 0.5. In the overall analyses of 80 sets of 10 post-chill rinses, sets with mean values less than 1.1 log 10 E. coli had lower incidence of Salmonella and Campylobacter compared to post-chill 10 carcass-sample sets with higher mean log10 E. coli levels. The distribution of log 10 E. coli levels within 10-carcass rinses at post-chill fit the logistic distribution, with a standard deviation of about 0.5. This information provides context for future studies regarding the use of E. coli levels on poultry carcasses as a measure of process control. To increase the power to detect relationships between E. coli levels on poultry carcasses and pathogens, examine inherent variability and other factors affecting microbial levels, further studies are recommended.