ESBL-E prevalence and genetic characteristics are described from isolates culture in The Netherlands between 2013 and 2015

Retail chicken meat is a potential source of Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae (ESBL-E). In the past decade vast national efforts were undertaken to decrease the antibiotic use in the veterinary sector, resulting in a total decrease of antibiotic sales in the sector of 58% between 2009 and the start of this study. The decrease in antibiotic use resulted in a decrease in ESBL-E prevalence in broilers. The current study investigates the ESBL-E prevalence in retail chicken meat purchased from different supermarkets in the Netherlands between December 2013 and August 2015 and epidemiological factors associated with the ESBL-E prevalence. In the current study 352 chicken meat samples were investigated for the presence of ESBL-E using selective culture methods leading to 346 evaluable samples. From these 346 samples, 188 (54,3%) samples were positive with 216 ESBL-E isolates (E. coli (n=204), K. pneumoniae (n=11) and E. fergusonii (n=1)). These were analysed in depth using whole-genome sequencing. The ESBL-E prevalence decreased from 68.3% in 2014 to 44.6% in 2015. The ESBL-E prevalence was lower in free-range chicken meat compared with conventional chicken meat and varied per supermarket chain. Pairwise isolate comparisons using whole-genome multilocus sequence typing (wgMLST) show that clustering of isolates occurs more frequently within supermarket chains compared with isolate comparisons across supermarket chains. In general, the frequency of clustering decreased with more time between the collection of the compared isolates. In conclusion, retail chicken meat still frequently harbours ESBL-E and as such remains a potential community source for ESBL-E in humans; however, the ESBL-E prevalence is decreasing over time.