Incidence of escherichia coli O157 in feces between naturally and conventionally produced beef in Southwest Kansas



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Changes in production methods of agricultural foods have evolved. Food and livestock are marketed in different ways including those from natural and conventional production methodologies. The objectives of this study were to evaluate the prevalence of Escherichia coli O157 between naturally and conventionally produced beef from a commercial feeding facility. Two sets of data for prevalence were obtained from two different southwest Kansas feed yards in two different trials. Positive samples from Feedlot A were evaluated for antimicrobial susceptibility. No differences (P = 0.8696) were found for prevalence of E. coli O157 between naturally- and conventionally-produced beef from samples obtained in both feedlots. A replication difference was detected (P < 0.001) with replications 1, 2 and 3 having lower prevalence of E. coli O157 as compared to replications 4 and 5. A production method by replication interaction was not detected (P = 0.3727). Feedlot A showed no difference (P = 0.5361) for prevalence of E. coli O157 with natural testing 5.11% positive and conventional testing 6.22% positive. No difference (P = 0.5747) for replication days or the production method by replication day interaction (P = 0.1608). Three of the positive isolates, all from naturally-produced cattle, from Feedlot A showed multi-drug resistance. Feedlot B showed positive results although no differences (P = 0.6568) were detected between naturally and conventionally produced beef for E. coli O157. Overall, 37.2% of the 500 samples were positive for E. coli O157:H7 with 42.4% of conventional samples and 32.0% of natural samples testing positive from Feedlot B. Sampling period did not affect (P = 0.8122) prevalence; day 1 had 38.4% positive, and 36.0% of samples tested positive on day 2. Comparing production type on sampling day, conventional positive samples dropped from day 1 to 2 (49.6% to 35.2%); however natural samples testing positive for E. coli increased from day 1 to 2 (27.2% to 36.8%). One pen of conventional samples was 100% positive. However, one pen of each treatment had 0% positive samples, both on day 2.
Although no significant differences were detected between naturally and conventionally-produced beef for E. coli O157, the high percentage of positive samples for each production type as well as the multi-drug resistant isolates from naturally produced beef indicated a need for the beef and animal health industries to continue pre and post-harvest intervention methods to control E. coli O157 prevalence in the food supply to prevent food-borne illnesses.