Prevalence of Extended-Spectrum β-Lactamase-Producing Escherichia coli on Bavarian Dairy and Beef Cattle Farms
ABSTRACTExtended-spectrum β-lactamase (ESBL)-producingEscherichia colistrains are believed to be widely distributed among humans and animals; however, to date, there are only few studies that support this assumption on a regional or countrywide scale. Therefore, a study was designed to assess the prevalence of ESBL-producingE. coliin dairy cows and beef cattle in the southern part of Bavaria, Germany. The study population included 30 mixed dairy and beef cattle farms and 15 beef cattle farms. Fecal samples, boot swabs, and dust samples were analyzed for ESBL-producingE. coliusing selective media. PCR was performed to screen for CTX-M andampCresistance genes. A total of 598 samples yielded 196 (32.8%) that contained ESBL-producingE. coli, originating from 39 (86.7%) of 45 farms. Samples obtained from mixed farms were significantly more likely to be ESBL-producingE. colipositive than samples from beef cattle farms (fecal samples,P< 0.001; boot swabs,P= 0.014; and dust samples,P= 0.041). A total of 183 isolates (93.4%) of 196 ESBL-producingE. coli-positive strains harbored CTX-M genes, CTX-M group 1 being the most frequently found group. Forty-six additional isolates containedampCgenes, and 5 of the 46 isolates expressed ablaCMY-2gene. The study shows that ESBL-producingE. colistrains are commonly found on Bavarian dairy and beef cattle farms. Moreover, to our knowledge, this is the first report of the occurrence ofblaCMY-2in cattle in Germany.