Extended-spectrum-β-lactamase- and AmpC-β-lactamase-producing Escherichia coli in Dutch broilers and broiler farmers

The aim of this study was to establish the prevalence of extended-spectrum -lactamase (ESBL)- and AmpC -lactamase-producing Escherichia coli at Dutch broiler farms and in farmers and to compare ESBL/AmpC-producing isolates from farmers and their animals. Twenty-five to 41 cloacal swabs collected from broilers at each of 26 farms and 18 faecal samples from 18 broiler farmers were analysed for determination of the presence of ESBL/AmpC-producing E. coli. ESBL/AmpC genes were characterized by microarray, PCR and sequencing. Plasmids were characterized by transformation and PCR-based replicon typing. Subtyping of plasmids was done by plasmid multilocus sequence typing or restriction fragment length polymorphism. E. coli genotypes were determined by multilocus sequence typing. Birds from all farms were positive for ESBL/AmpC-producing E. coli, and on 22/26 farms the within-farm prevalence was epsilon 80. Six of 18 farmers carried isolates containing ESBL/AmpC genes bla(CTX-M-1), bla(CMY-2) and/or bla(SHV-12), which were also present in the samples from their animals. In five of these isolates, the genes were located on identical plasmid families [IncI1 (n3), IncK (n1) or IncN (n1)], and in isolates from two farmers the genes were carried on identical plasmid subtypes (IncI1 ST12 and IncN ST1, where ST stands for sequence type) as in the isolates from their animals. This study shows a high prevalence of birds carrying ESBL/AmpC-producing E. coli at Dutch broiler farms and a high prevalence of ESBL/AmpC-producing E. coli in farmers. This is undesirable due to the risk this poses to human health. Future research should focus on identification of the source of these isolates in the broiler production chain to make interventions resulting in reduction of these isolates possible.