Occurrence of and risk factors for extended-spectrum cephalosporin-resistant Enterobacteriaceae determined by sampling of all Norwegian broiler flocks during a six month period

All broiler flocks reared and slaughtered in Norway from May-October 2016 (n = 2110) were screened for the presence of extended-spectrum cephalosporin (ESC) -resistant Enterobacteriaceae. Furthermore, we investigated possible risk factors for occurrence of such bacteria in broiler flocks. The odds of a flock being positive for ESC-resistant Enterobacteriaceae increased if the previous flock in the same house was positive, and if the flock was reared during September-October. However, we cannot exclude seasonal fluctuations in occurrence of ESC-resistant Enterobacteriaceae during the months November to April. The overall occurrence of ESC-resistant Enterobacteriaceae was 10.4%, and primarily linked to the presence of blaCMY (82.6%) in positive isolates. We describe the first findings of Escherichia coli with blaCTX-M-1, Klebsiella pneumoniae with both blaCTX-M-15 and blaSHV-12, and K. pneumoniae with blaCMY isolated from Norwegian broiler production. This study gives us a unique overview and estimate of the true occurrence of ESC-resistant Enterobacteriaceae in Norwegian broilers over a six-month period. To the best of our knowledge, this is the most comprehensive study performed on the occurrence of ESC-resistant Enterobacteriaceae in a broiler population.本研究对2016年5月至10月期间挪威境内所有饲养并屠宰的肉用鸡群（n=2110）开展筛查，以检测超广谱头孢菌素（extended-spectrum cephalosporin, ESC）耐药肠杆菌科（Enterobacteriaceae）细菌的携带情况。此外，本研究还探究了肉用鸡群中此类细菌检出的潜在危险因素。当同一鸡舍内的前一批肉鸡群呈阳性，且本次鸡群的饲养周期处于9月至10月时，该鸡群检出ESC耐药肠杆菌科细菌的风险比值显著升高。不过，本研究无法排除11月至次年4月期间，ESC耐药肠杆菌科细菌的检出情况存在季节波动。ESC耐药肠杆菌科细菌的总体检出率为10.4%，阳性分离株中主要携带blaCMY基因（占比82.6%）。本研究首次报道了从挪威肉鸡养殖体系中分离得到的携带blaCTX-M-1基因的大肠埃希菌（Escherichia coli）、同时携带blaCTX-M-15与blaSHV-12基因的肺炎克雷伯菌（Klebsiella pneumoniae），以及携带blaCMY基因的肺炎克雷伯菌。本研究为挪威肉鸡群在6个月周期内ESC耐药肠杆菌科细菌的实际检出情况提供了独特的全景式概述与量化评估。据我们所知，本研究是针对肉鸡群中ESC耐药肠杆菌科细菌检出情况开展的最为全面的相关研究。