中国德尔卑沙门菌耐药及群体遗传特征初步分析

Exploration of antibiotic resistance and population genetic characteristics of Salmonella Derby in China

目的分析不同来源德尔卑沙门菌的耐药特征、耐药机制及基因组相似性,初步揭示我国德尔卑沙门菌的群体遗传学特征,发现可能的传播规律或潜在传播途径,为加强沙门菌病监测及防控策略制定提供一定参考。方法对201株德尔卑沙门菌进行16种抗生素的药物敏感性试验,并对所有菌株进行全基因组测序。最后结合公开数据库中的134株德尔卑沙门菌基因组序列,对335株德尔卑沙门菌进行耐药基因型别和多位点序列分型(MLST)分析,并构建基于核心基因组单核苷酸多态性的系统发育树进行遗传进化分析。结果201株德尔卑沙门菌对16种抗生素呈现不同程度的耐药,总耐药率为97.51%。不同来源(人、动物、食品)的德尔卑沙门菌对不同种类抗生素耐药率差异有统计学意义(均P<0.05)。335株德尔卑沙门菌携带耐药基因38种,磷霉素类耐药基因fosA7携带率为100.00%,氨基糖苷类耐药基因aac(6')-Iaa携带率为99.70%。不同种类抗生素耐药基因和耐药表型一致性存在差异,除氨基糖苷类和氯霉素类,其他种类抗生素一致性较好。MLST显示,334株德尔卑沙门菌为ST40型。系统发育树显示存在动物和人、食品和人之间交叉感染的风险以及动物带菌远距离跨省播散的可能,但还需要进一步的流行病学研究。结论我国德尔卑沙门菌耐药形势严峻,并且存在交叉传播的风险,提示应加强综合监测及风险评估,防止耐药菌株及耐药元件在动物、食品、人链条中的播散。

Objective To characterize the antimicrobial resistance,resistance machanism and population genetics of Salmonella(S.)Derby in China,preliminarily reveal the population genetic characteristics of S.Derby in China,discover possible transmission patterns or potential transmission pathways,and provide certain reference for strengthening S.disease monitoring and developing prevention and control strategies.Methods A total of 201 strains of S.Derby from different areas in China were used for the susceptible tests to 16 antibiotics and whole-genome sequencing.Finally,combined with the genome sequences of 134 strains of S.Derby from public databases,335 strains of S.Derby were used for resistance genotype analysis and multi-locus sequence typing(MLST),and a phylogenetic tree based on the core genome single nucleotide polymorphisms was constructed for evolutionary analysis.Results The results showed that 201 strains of S.Derby showed resistance to 16 kinds of antibiotics at different levels.The overall resistance rate was 97.51%.The resistance rates to antibiotics varied in S.Derby from different sources(human,animal,and food),the differences were significant(all P<0.05).A total of 38 resistance genes were carried by 335 strains of S.Derby,of which,fosfomycin gene fosA7 was found in all the strains(100.00%)and aminoglycoside genes aac(6')-Iaa accounted for 99.70%.The consistency of resistance genes and phenotypes varied with antibiotics.Except aminoglycosides and chloramphenicol,the consistencies of resistance genes and phenotypes for other antibiotics were high.MLST showed that 334 strains of S.Derby belonged to ST40.Phylogenetic trees indicated the risk for cross-infection between animal and human,food and human,and the possibility of long-distance interprovincial transmission of the bacteria by animal,to which further epidemiological studies are needed.Conclusions The drug resistance of S.Derby is serious in China and the risk for cross-transmission between human and animal or food exists.It is necessary to establish and strengthen the comprehensive surveillance and risk assessment to prevent the spread of antibiotic resistant strains or elements through animal,food and human chains.