摘要

弯曲杆菌是一种主要的食源性致病菌，以往的研究表明，我国食品生产动物的弯曲杆菌对庆大霉素的耐药率越来越高。我国庆大霉素耐药的分子流行病学和遗传机制尚不清楚。对2014年采集的607株鸡和猪源弯曲菌进行了分析，发现空肠弯曲菌和大肠弯曲菌对庆大霉素耐药率分别为15.6 % ( 25 / 160 )和79.9 % ( 357 / 447 )。对庆大霉素耐药基因的PCR检测表明，aph ( 2″) - If比以前鉴定的aacA / aphD基因更为流行，已成为弯曲杆菌庆大霉素耐药的主要决定因素。转化和全基因组测序以及远程PCR发现aph ( 2″) - If位于插入两个保守基因Cj0299和panB之间的染色体片段上。将aph ( 2″) - If克隆到庆大霉素敏感空肠球菌NCTC 1116 8中，证实了其对庆大霉素和卡那霉素的高水平耐药作用。脉冲场凝胶电泳分子分型表明，特定克隆的区域扩增和水平传播都参与了aph ( 2″) - If基因在弯曲杆菌中的传播。据我们所知，这是第一篇报道描述染色体编码aph ( 2″) - If基因在弯曲杆菌中的高流行率。该基因的高流行率和优势可能是由于我国食用动物生产中氨基糖苷类抗生素的使用，并可能损害庆大霉素作为弯曲杆菌相关全身感染治疗剂的用途。

Campylobacter is a major foodborne pathogen, and previous studies revealed thatCampylobacter isolates from food-producing animals are increasingly resistant to gentamicin in China. The molecular epidemiology and genetic mechanisms responsible for gentamicin resistance in China have not been well understood. In this study, 607 Campylobacter isolates of chicken and swine origins collected in 2014 were analyzed, revealing that 15.6% (25/160) of the Campylobacter jejuniisolates and 79.9% (357/447) of the Campylobacter coli isolates were resistant to gentamicin. PCR detection of the gentamicin resistance genes indicated thataph(2″)-If was more prevalent than the previously identified aacA/aphD gene and has become the dominant gentamicin resistance determinant in Campylobacter. Transformation and whole-genome sequencing as well as long-range PCR discovered that aph(2″)-If was located on a chromosomal segment inserted between two conserved genes, Cj0299 and panB. Cloning of aph(2″)-If into gentamicin-susceptible C. jejuni NCTC 11168 confirmed its function in conferring high-level resistance to gentamicin and kanamycin. Molecular typing by pulsed-field gel electrophoresis suggested that both regional expansion of a particular clone and horizontal transmission were involved in the dissemination of theaph(2″)-If gene in Campylobacter. To our knowledge, this is the first report describing the high prevalence of a chromosomally encoded aph(2″)-If gene inCampylobacter. The high prevalence and predominance of this gene might be driven by the use of aminoglycoside antibiotics in food animal production in China and potentially compromise the usefulness of gentamicin as a therapeutic agent for Campylobacter-associated systemic infection.

http://aac.asm.org/content/61/5/e00112-17.short