一株同时携带optrA和cfrC基因的猪源多重耐药结肠弯曲菌的全基因组测序

Whole genome sequencing of a porcine multiresistant Campylobacter coli strain carrying both optrA and cfrC

摘要:

【背景】弯曲菌(Campylobacter)是一种世界范围内能引起胃肠炎的最常见食源性病原菌，对临床上重要的抗菌药物耐药越来越严重，对食品安全和公共健康造成重大威胁。【目的】研究一株同时携带optrA和cfrC基因的猪源结肠弯曲菌(Campylobacter coli)耐药表型和耐药基因，同时对该菌全基因组特征、毒力基因分布情况以及optrA和cfrC基因环境进行分析。【方法】采用琼脂平板稀释法进行最低抑菌浓度(minimal inhibitory concentration, MIC)测定，并且对该菌进行全基因组测序。【结果】该菌株对四环素、克林霉素、阿奇霉素、氟苯尼考和利奈唑胺呈现高度耐药，对环丙沙星和庆大霉素敏感。全基因组测序得到一条大小为1 436 486 bp的环状DNA (GC含量为31.63%)，携带四大类抗生素中共计12种耐药基因，均定位于染色体上，其中氨基糖苷类耐药基因数量最多。此外，携带包含黏附、侵袭和移动等相关毒力基因83个，其中与移动相关的毒力基因数量最多。对4个基因岛分析发现，基因岛GIs002和GIs003中含有耐药基因序列，cfrC位于基因岛GIs002上，与aph(3')-IIIa相连，两侧与转座酶相连，optrA位于染色体上，在其上、下游两侧与插入序列integrase/IS607 family相连，转座酶和插入序列可介导耐药基因水平转移。【结论】本研究通过全基因组测序分析了多重耐药结肠弯曲菌的基因组信息以及存在的耐药及毒力基因情况，可移动遗传元件(转座酶和插入序列)在结肠弯曲菌耐药传播中起着重要作用，该研究结果为弯曲菌耐药风险评估提供了参考依据。

Abstract:

[Background] Campylobacter is a common group of foodborne pathogens that can cause gastroenteritis in the world. It is increasingly resistant to clinically important antibiotics and poses a serious threat to food safety and public health. [Objective] To investigate the resistance phenotype and genes of a Campylobacter coli strain carrying both optrA and cfrC, the whole genome characteristics of the strain, the distribution of virulence genes, and the gene environments of optrA and cfrC. [Methods] Agar dilution method was employed to determine the minimal inhibitory concentrations (MIC). Whole genome sequencing (WGS) was carried out to sequence the DNA of the strain. [Results] The strain was highly resistant to tetracycline, clindamycin, azithromycin, florfenicol, and linezolid, and sensitive to ciprofloxacin and gentamicin. WGS identified a circular DNA with a size of 1 436 486 bp (GC content of 31.63%), which carried 12 resistance genes involving four major categories of antibiotics. All of the 12 genes were detected on the chromosome, most of which were aminoglycoside resistance genes. A total of 83 virulence genes involved in adherence, invasion and motility were identified, and most of them were associated with motility. The gene islands GIs002 and GIs003 contained resistance genes. CfrC was located on the GIs002, linked with aph(3')-Ⅲa and flanked by two transposons. OptrA was located on chromosome and connected to the insertion sequence Integrase/IS607 family at upstream and downstream sides. Transposon and insertion sequence could mediate the horizontal transfer of resistance genes. [Conclusion] The genome information, resistance genes, and virulence genes of a multiresistant C. coli strain were analyzed by WGS. The mobile genetic elements (transposase and insertion sequence) played an important role in the transmission of antibiotic resistance of C. coli. The findings provide basic information for risk assessment of antibiotic resistance of Campylobacter.