沙门氏菌CTX-M型超广谱β-内酰胺酶基因分型及变异研究

Distribution and variation of CTX-M extended-spectrum β-lactamase genes in Salmonella

目的通过对不同血清型中沙门氏菌中CTX-M型超广谱β-内酰胺酶分子基因型别、脉冲场凝胶电泳(PFGE)溯源分析及CTX-M氨基酸位点变异情况,研究CTX-M各型别流行特征及在超级耐药克隆中的作用。方法对来源于江苏及周围地区的61株CTX-M阳性的肠炎沙门氏菌(S.enteritidis)、印第安纳沙门氏菌(S.indiana)、汤卜逊沙门氏菌(S.thompson)等进行CTX-M型别鉴定、PFGE分子分型、全基因测序对不同型别CTX-M氨基酸位点变异分析。结果61株菌株分为3个CTX-M群6个型。S.indiana含有6种CTX-M基因型,主要型别是CTX-M-65和CTX-M-55;S.enteritidis和S.thompson主要型分别为CTX-M-55、CTX-M-65。PFGE聚类分型有19个型。A2型是携带CTX-M-55型S.enteritidis;B4、B8、B9型是携带CTX-M-55型或CTX-M-65型的S.indiana;D2为携带CTX-M-65型的S.thompson。CTX基因组序列分析显示,在CTX-M-1群、CTX-M-9群、CTX-M-64群易变化氨基酸位点分别是4、3、12个。结论本地区主要CTX型别为CTX-M-55型或CTX-M-65型,S.indiana是CTX基因主要来源。位于质粒上的CTX-M基因复杂且多变是S.indiana超级耐药克隆形成并广泛流行重要原因之一。

To learn the epidemic characterizations and the role of CTX-M genes in the resistant clones in Jiangsu and surrounding areas, 61 Salmonella isolates including S. enteritidis, S. indiana, S.thompson with CTX-M genes identified with CTX-M typing, PFGE, and the amino acid site variation with different CTX-M types. There were 3 CTX-M groups and 6 CTX-M types among 61 isolates. There were 6 types, mainly CTX-M-65 and CTX-M-55, in S. indiana clone, while CTX-M-55 and CTX-M-65 was mainly in S. enteritidis clone and S.thompson clone, respectively. There were 19 PFGE genotypes based on Dendrogram including A2, S. Enteritidis carried CTX-M-55, B4, B8, B9, S. indiana carried CTX-M-55 or CTX-M-65, and D2, S.thompson carried CTX-M-65. Analyzing with whole-genome sequencing, there were 4, 3, and 12 labile amino acid sites in CTX-M-1group, CTX-M-9 group, and CTX-M-64 group, respectively. The CTX-M-55 and CTX-M-65 were the main CTX genotypes in Salemonella isolates in Jiangsu and surr ounding areas, which were mainly from S. indiana clone. The CTX-M gene located on plasmids, which were various and heterogeneous, was one of contrbuting factors that results in the forming and transmission of the super-multidrug-resistant S. indiana clone.