Herd prevalence of E nterobacteriaceae producing CTX ‐ M ‐type and CMY ‐2 β ‐lactamases among J apanese dairy farms

Aims To determine the herd prevalence of E nterobacteriaceae producing CTX ‐ M ‐type extended‐spectrum β ‐lactamases ( ESBL s) among 381 dairy farms in J apan. Methods and Results Between 2007 and 2009, we screened 897 faecal samples using BTB lactose agar plates containing cefotaxime (2 μg ml −1 ). Positive isolates were tested using ESBL confirmatory tests, PCR and sequencing for CTX ‐ M , A mp C , TEM and SHV . The incidence of E nterobacteriaceae producing CTX ‐ M ‐15 ( n  = 7), CTX ‐ M ‐2 ( n  = 12), CTX ‐ M ‐14 ( n  = 3), CMY ‐2 ( n  = 2) or CTX ‐ M ‐15/2/14 and CMY ‐2 ( n  = 4) in bovine faeces was 28/897 (3·1%) faecal samples. These genes had spread to E scherichia coli ( n  = 23) and three genera of E nterobacteriaceae ( n  = 5). Herd prevalence was found to be 20/381 (5·2%) dairy farms. The 23 E . coli isolates showed clonal diversity, as assessed by multilocus sequence typing and pulsed‐field gel electrophoresis. The pandemic E . coli strain ST 131 producing CTX ‐ M ‐15 or CTX ‐ M ‐27 was not detected. Conclusions Three clusters of CTX ‐ M ( CTX ‐ M ‐15, CTX ‐ M ‐2, CTX ‐ M ‐14) had spread among Japanese dairy farms. Significance and Impact of the Study This is the first report on the prevalence of multidrug‐resistant CTX ‐ M ‐15–producing E . coli among J apanese dairy farms.