Cefotaxime-resistant Escherichia coli in broiler farms-A cross-sectional investigation in Germany

- In 34 broiler farms in Germany 59 flocks were investigated and 295 samples were analysed for cefotaxime resistant E. coli.
- In all flocks and subsequently all farms, at least one sample contained cefotaxime resistant E. coli.
- A high proportion of all sample types was positive for CTX resistant E. coli (faeces: 82%; boot swabs: 80% and dust samples: 63%).
- In addition to other studies our study supports the finding that CTX resistance is a good proxy for the presence of ESBL/pAmpC-beta-lactamases.
- Sample results of two flocks on the same farm are comparable, which supports the assumption that the flocks on one farm are not independent.

In this investigation the farm prevalence of cefotaxime-resistant Escherichia coli (CREC) in German broiler farms was evaluated. In total, 59 flocks on 34 broiler farms were sampled in four agricultural regions of Germany. Per broiler flock, three faecal samples, a pair of boot swabs and one dust sample were taken and examined for the presence of CREC. After pre-enrichment of sample material in Luria-Bertani-broth, the broth was streaked onto MacConkey agar containing 1 mg/l cefotaxime (CTX). CREC isolates were detected in at least one sample from each flock resulting in a farm prevalence of 100%. The proportion of positive samples was high in all three sample types. Of 177 collective faecal samples 81.9% were positive, of 59 boot swabs and 59 dust samples 79.7% and 62.7% were positive. In conclusion, the prevalence of broiler farms with cefotaxime-resistant E. coli in Germany is very high. We suggest that the analysis of collective faecal samples is sufficient to determine the CREC farm status. In addition to other studies our study supports the finding that cefotaxime resistance is a good proxy for the presence of ESBL- or plasmidic AmpC-beta-lactamases.