National Veterinary Institute, Uppsala, Sweden.
Norwegian Veterinary Institute, Oslo, Norway.
Vet Microbiol. 2018 Jan;213:123-128. doi: 10.1016/j.vetmic.2017.11.015. Epub 2017 Nov 21.
The intestinal flora of healthy broilers can contain Escherichia coli resistant to extended spectrum cephalosporins (ESC) and fluoroquinolones (FQ), representing a possible public health problem. We investigated the clonal epidemiology of E. coli with reduced susceptibility to ESC or FQ in broilers in three Nordic countries interconnected by a common source of breeding animals. Isolates (n = 319 and n = 132 non-wild type for ESC and FQ, respectively) from Norwegian, Swedish and Icelandic production originated mainly from the intestinal flora of broilers at the age of 20-35 days. Genetic relationships were investigated by ten loci multilocus variable number tandem repeat analyses (MLVA) and representative isolates of inter-Nordic clusters were subjected to multilocus sequence typing (MLST). Antimicrobial susceptibility data based on minimum inhibitory concentrations was compiled. Approximately one third of the ESC non-wild type isolates, including isolates from all three countries, clustered together. These isolates belonged to sequence type (ST) 38 and contained bla. The FQ non-wild type isolates were more genetically diverse, but related isolates occurred in more than one country. MLST typing showed clusters belonging to ST10, ST355, ST349, ST665 and ST93. Our study demonstrated inter-Nordic distribution of E. coli ST38 with bla suggesting clonal proliferation as a contributing factor for spread of ESC resistance in the broiler production. The international trade in breeding material may explain introduction of resistant E. coli. The reason for their success and the success of certain clonal lineages in broiler production not exposed to antimicrobial selection pressure is currently unknown.
健康肉鸡的肠道菌群可能含有对广谱头孢菌素（ESC）和氟喹诺酮类药物（FQ）具有耐药性的大肠杆菌，这代表了一个潜在的公共卫生问题。我们研究了三个北欧国家肉鸡中对 ESC 或 FQ 敏感性降低的大肠杆菌的克隆流行病学，这些国家通过共同的种畜来源相互关联。来自挪威、瑞典和冰岛生产的分离株（n=319 和 n=132 分别为 ESC 和 FQ 的非野生型）主要来自 20-35 日龄肉鸡的肠道菌群。通过 10 个基因座多位点可变数串联重复分析（MLVA）研究遗传关系，并对国际间聚类的代表性分离株进行多位点序列分型（MLST）。根据最小抑菌浓度编译了抗生素敏感性数据。大约三分之一的 ESC 非野生型分离株，包括来自所有三个国家的分离株，聚集在一起。这些分离株属于序列型（ST）38 并携带 bla。FQ 非野生型分离株具有更多的遗传多样性，但在多个国家都存在相关分离株。MLST 分型显示属于 ST10、ST355、ST349、ST665 和 ST93 的聚类。我们的研究表明，携带 bla 的大肠杆菌 ST38 在北欧国家之间分布，提示克隆增殖是 ESC 耐药性在肉鸡生产中传播的一个促成因素。种畜的国际贸易可能解释了耐药大肠杆菌的传入。它们成功的原因以及某些克隆谱系在未暴露于抗菌选择压力的肉鸡生产中的成功原因目前尚不清楚。
