Yang Wanna, Zhang Maojun, Zhou Jiyuan, Pang Lili, Wang Guiqiang, Hou Fengqin
1 Department of Infectious Diseases and the Center for Liver Diseases, Peking University First Hospital , Beijing, China .
2 State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention , Chinese Center for Disease Control and Prevention, Beijing, China .
Foodborne Pathog Dis. 2017 Jul;14(7):386-392. doi: 10.1089/fpd.2016.2223.
We assessed the susceptibility of 182 Campylobacter jejuni isolates from patients with diarrhea to eight antibiotics and analyzed the molecular mechanisms of ciprofloxacin resistance as well as the genetic characteristics based on multilocus sequence typing (MLST). The C257T mutation was found on the quinolone resistance-determining region (QRDR) of the gyrA gene in all ciprofloxacin-resistant strains. Mutations on the QRDR of the gyrB gene were silent. A total of 74 strains had 7 inverted repeat (IR) (a 16-bp IR on the intergenic region between cmeR and cmeABC) mutation polymorphisms. Compared with strains without the IR mutations, strains with the IR mutations had higher resistance rates to ciprofloxacin (94.6% vs. 83.3%), nalidixic acid (94.6% vs. 83.3%), tetracycline (98.6% vs. 85.2%), doxycycline (91.9% vs. 71.3%), florfenicol (59.5% vs. 17.6%), chloramphenicol (25.7% vs. 4.6%), gentamicin (16.2% vs. 3.7%), and multidrug resistance than those without IR mutations (all p < 0.05). With C257T mutation alone, 89.9% strains with minimum inhibitory concentration (MIC) values focused on 16, 32, and 64 μg/mL, whereas strains with C257T mutation in combination with the IR mutations had a higher ciprofloxacin resistance level with 88.6% MIC values focused on 64, 128, and 512 μg/mL (p < 0.0001). The strains in this study showed a high genetic variability based on MLST with 117 sequence types (STs), 37 of which were novel. CC-21 was the most common clonal complex (CC) followed by CC-353 and CC-45. No association was found between STs and ciprofloxacin resistance. In conclusion, the C257T mutation on gyrA was the major mechanism for ciprofloxacin resistance, and the C257T mutation in combination with the IR mutations might result in more severe ciprofloxacin resistance to C. jejuni.
我们评估了182株从腹泻患者中分离出的空肠弯曲菌对8种抗生素的敏感性，并基于多位点序列分型（MLST）分析了环丙沙星耐药的分子机制以及遗传特征。在所有环丙沙星耐药菌株的gyrA基因喹诺酮耐药决定区（QRDR）发现了C257T突变。gyrB基因QRDR上的突变是沉默的。共有74株菌株存在7种反向重复序列（IR）（cmeR与cmeABC之间基因间区域的16bp IR）突变多态性。与无IR突变的菌株相比，有IR突变的菌株对环丙沙星（94.6%对83.3%）、萘啶酸（94.6%对83.3%）、四环素（98.6%对85.2%）、强力霉素（91.9%对71.3%）、氟苯尼考（59.5%对17.6%）、氯霉素（25.7%对4.6%）、庆大霉素（16.2%对3.7%）的耐药率更高，且多药耐药性也高于无IR突变的菌株（所有p<0.05）。仅存在C257T突变时，89.9%的菌株最小抑菌浓度（MIC）值集中在16、32和64μg/mL，而同时存在C257T突变和IR突变的菌株对环丙沙星的耐药水平更高，88.6%的MIC值集中在64、128和512μg/mL（p<0.0001）。基于MLST分析，本研究中的菌株显示出较高的遗传变异性，共有117种序列类型（STs），其中37种为新发现的类型。CC-21是最常见的克隆复合体（CC），其次是CC-353和CC-45。未发现STs与环丙沙星耐药之间存在关联。总之，gyrA基因上的C257T突变是环丙沙星耐药的主要机制，C257T突变与IR突变共同作用可能导致空肠弯曲菌对环丙沙星产生更严重的耐药性。
