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Validation of Sampling Methods to Determine the Prevalence of E. coli O157:H7 in Beef Feedlot Cattle


The objective of this study was to determine ideal sampling methods to estimate the prevalence
of E. coli O157:H7 and Salmonella in feedlot cattle to potentially provide standardization of
methods for future epidemiological and intervention studies.

More information

Study 1: Feedlot cattle were sampled at various sites to determine the best location for detecting E. coli O157 and Salmonella on the live animal if either is present. Samples analyzed included feces, swab of the mucosa just proximal to the rectoanal junction, swab of the oral cavity, and hide swab of the back, flank, hock, perineum, ventral midline and neck region. E. coli O157 was recovered from at least one site from 14.9% of animals. In our study, the greatest estimates of prevalence were obtained from feces, 46.2%, perineum swabs, 38.5%, and hock swabs, 38.5% among positive animals. Salmonella was recovered from at least one site from all animals. The sites of greatest recovery were the oral cavity (94%), perineum (88%), and hock (94%). Interesting, feces, 50%, had the lowest recovery rate. The best hide sites for recovery were similar for Salmonella and E. coli O157; however, feces was the best overall sample for detection of E. coli O157 but the worst for detection of Salmonella.
Study 2: E. coli O157 does not appear to be evenly distributed in fecal material. When the number of sample sites analyzed per pat increased, so did the estimate of prevalence. If only one site per pat was analyzed, the estimate of prevalence was least (13.3%). This estimate of prevalence increased with additional sites within the pat that were analyzed. If 2, 3, 4, or 5 sites per pat were analyzed for E. coli O157, the estimates of prevalence were 17.1, 19.4, 21.3, and 22.9%. It was hoped that a composite, homogenized sample from all 5 sites would have resulted in improved estimates of prevalence. If so, only one sample need be analyzed versus 5. However, the estimate of prevalence based on the composite sample was 14.6% and not different from the estimate from sampling 1 site.

<P> For complete projects details, view the <a href="…; target="_blank">Project Summary. </a>

Loneragan, Guy ; Brashears, Mindy
Texas Tech University
West Texas A&M University
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