Herd prevalence of Enterobacteriaceae producing CTX-M-type and CMY-2 β-lactamases among Japanese dairy farms



Mamoru Ohnishi, Veterinary Clinical Laboratory, Nemuro District Agricultural Mutual Aid Association, 11-5 Minami, 5 Nishi, Nakashibetsu-cho, Shibetsu-gun, Hokkaido 086-1105, Japan. E-mail: monishi@kind.ocn.ne.jp



To determine the herd prevalence of Enterobacteriaceae producing CTX-M-type extended-spectrum β-lactamases (ESBLs) among 381 dairy farms in Japan.

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, AmpC, TEM and SHV. The incidence of Enterobacteriaceae producing CTX-M-15 (= 7), CTX-M-2 (= 12), CTX-M-14 (= 3), CMY-2 (= 2) or CTX-M-15/2/14 and CMY-2 (= 4) in bovine faeces was 28/897 (3·1%) faecal samples. These genes had spread to Escherichia coli (= 23) and three genera of Enterobacteriaceae (= 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 ST131 producing CTX-M-15 or CTX-M-27 was not detected.


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 Japanese dairy farms.