4例多重耐药非伤寒沙门菌的耐药基因和分子分型

目的 研究中山市多重耐药非伤寒沙门菌株的耐药基因和分子分型特征。 方法 分析2015年7月中山市博爱医院培养出的4例多重耐药NTS菌株的药敏结果,并且对该4例菌株进行脉冲场凝胶电泳分型（PFGE）多位点序列分型技术（MLST）和全基因组测序分析（WGS）,并在此基础上对4例菌株进行差异性分析,量化菌株之间的遗传发育距离,确定病例菌株之间的关系。 结果 4例菌株均为鼠伤寒沙门菌变种,并且均为多重耐药菌株,菌株S2、S3和S4药敏结果几乎相同,与S1差异较大。PFGE可将4例菌株分为两个大组（组A和组B）,菌株S2、S3、S4落到同一个大组B中,菌株S2、S3、S4抗原式相同并均与S1有差异;MLST发现菌株S1为ST19型,菌株S2、S3、S4为ST34型。菌株S1抗药基因谱与菌株S2、S3、S4差异大,菌株S2、S3和S4 均有blaCTX-M-55基因。菌株S2、S3和S4的WGS形似度非常高,几乎可确定为同一来源。 结论 4例多重耐药菌株均为鼠伤寒沙门菌变种,菌株S2、S3和S4为同一来源。 blaCTX-M-55基因可能是造成本次中山市NTS多重耐药的主要原因之一。

Drug resistance gene and molecular typing study on four multi-drug resistant nontyphoidal Salmonella

Objective To study the drug resistance gene and molecular typing of multi-drug resistant nontyphoidal Salmonella (NTS) strains in Zhongshan City. Methods The drug sensitivity results of 4 multi-drug resistant NTS strains were cultured in BOAI Hospital of Zhongshan in July 2015, and the results of drug sensitivity were analyzed. Pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and whole genome sequencing (WGS ) were performed on the 4 strains, and whole genome sequencing was carried out for the 4 strains. On this basis, the differences among the 4 strains were analyzed to quantify the genetic and developmental distance among them, and to determine the relationship among the strains. Results All 4 strains were strains of Salmonella typhimurium var. typhimurium and were multidrug resistant. The results of drug sensitivity of strains S2, S3 and S4 were almost the same, which was different from S1. According to the PFGE findings, the Salmonella typhimurium strains could be divided into two large groups A and B. Strains S2, S3 and S4 belonged to cluster B. The results of PFGE showed that S2, S3 and S4 had the same antigenic formula and were different from S1. The MLST analysis showed that strain S1 belonged to genotype ST19, while strains S2, S3 and S4 all belonged to genotype ST34. The phylogenesis analysis revealed that strain S1 had distant genetic relationship with strains S2, S3 and S4. The strains S2, S3, S4 all had the blaCTX-m-55 gene. The WGS results of strains S2, S3 and S4 were very similar. They could be almost identified as the same source. Conclusion All the 4 multiple drug resistant strains are Salmonella typhimurium strains, and strains S2, S3, S4 are almost determined as the same source. The blaCTX-M-55 gene may be one of the main causes of NTS multidrug resistance in Zhongshan City.