An Abattoir-Based Study on the Prevalence of Salmonella Fecal Carriage and ESBL Related Antimicrobial Resistance from Culled Adult Dairy Cows in Wuhan, China.

The objective of this study was to estimate the fecal carriage of Salmonella spp. among culled adult dairy cows presented to an abattoir in Wuhan, China and to evaluate their antimicrobial resistance profiles. Rectal swabs from 138 culled cows were cultured. Laboratory analysis involved the identification of Salmonella, the susceptibility assessment and the presence of Extended Spectrum beta-lactamases and mcr genes in the isolates. An overall prevalence of Salmonella of 29.0% was recorded with 63.4% (26/41) and 2.4% (1/41) of the isolates identified as S. Typhimurium and S. Dublin, respectively. The occurrence of Salmonella was higher (odd ratios: 3.3) in culled cows originating from the northeast zone of China than cows originating from the central and north zones. Twenty multi-drug resistant strains (resistant to three or more antimicrobial agents) were detected (48.8%) and overall, a high resistance to ampicillin (36/41) and tetracycline (15/41) was observed. Extended Spectrum beta-lactamases phenotypes were found in 7/41 isolates, of which all contained the bla(CTX-M) resistance gene, and no mcr genes were found by polymerase chain reaction. The high prevalence of Salmonella fecal carriage and antimicrobial resistance may contribute to an increased risk of Salmonella transmission to food.