High prevalence of extended-spectrum-β-lactamase-producing Enterobacteriaceae in organic and conventional retail chicken meat, Germany

To determine the prevalence of extended-spectrum -lactamase (ESBL) production in Enterobacteriaceae in retail chicken meat in Germany. A total of 399 chicken meat samples from nine supermarket chains, four organic food stores and one butchers shop in two geographically distinct regions (Berlin and Greifswald) were screened for ESBL production using selective agar. Phenotypic ESBL isolates were tested for bla(TEM), bla(CTX-M) and bla(SHV) genes using PCR and DNA sequencing. Antibiotic coresistances were determined and strain typing was performed using PCR-based phylogenetic grouping and XbaI-PFGE. A total of 185 confirmed ESBL isolates were obtained from 175 samples (43.9) from all tested sources. The majority of isolates were Escherichia coli producing ESBL types SHV-12 (n82), CTX-M-1 (n77) and TEM-52 (n16). No differences could be observed in the prevalence of ESBL producers between organic and conventional samples. 73.0 of the ESBL producers showed coresistance to tetracycline, 35.7 to co-trimoxazole and 7.6 to ciprofloxacin. Strain typing of selected E. coli isolates from Berlin revealed identical macrorestriction patterns for several isolates from samples taken from the same stores. This is the first comprehensive study from Germany showing a high prevalence of TEM-, CTX-M- and SHV-type ESBLs in Enterobacteriaceae isolated from retail chicken meat. The high rate of coresistance to different classes of antibiotics in the ESBL producers might reflect the common veterinary usage of these and related substances. There is an urgent need to further evaluate the role of poultry in the transmission of highly resistant ESBL-producing bacteria in humans.