不同来源菌株中8种mcr亚型基因筛查及阳性菌株药敏分析

Screen of 8 subtypes of the mcr gene in isolates from different clinical specimens and analysis on the drug-sensitivity of positive strains

目的了解8种mcr亚型基因在不同来源临床标本细菌中的分布及阳性菌株的药敏情况。方法采用PCR法分别对128株粪便标本分离的耐黏菌素菌株和130株临床感染标本分离的耐碳青霉烯菌株检测8种mcr亚型基因及mcr阳性菌株的碳青霉烯酶基因,对阳性基因扩增产物进行测序分析;对mcr阳性的菌株进行质谱鉴定和药敏分析;质粒接合实验验证mcr基因的可转移性;采用PCR法对质粒进行分型和检测12种毒力基因的存在情况。结果128株耐黏菌素菌株均没有发现mcr2、mcr3、mcr4、mcr5、mcr6、mcr7、mcr8基因;130株耐碳青霉烯菌株中没有发现mcr2、mcr3、mcr4、mcr5、mcr6、mcr7、mcr8基因。该mcr1阳性株不携带碳青霉烯酶基因,药敏结果显示多重耐药性,对黏菌素为中介,对磺胺类、喹诺酮、碳青霉烯类、绝大部分头孢类药物等耐药,产超广谱β-内酰胺酶(ESBLs)。mcr1阳性菌株质粒接合成功;mcr1阳性菌株携带6种质粒型及3种毒力基因。结论在肠道中耐黏菌素菌株和临床上耐碳青霉烯分离株中mcr1存在一定的流行率,其余7型的mcr基因流行率尚低;为探究mcr基因与ESBLs和碳青霉烯酶之间的关系提供一定的临床依据。

Objective To investigate the prevalence of 8 subtypes of the mcr gene in bacteria from different sources of clinical samples and the drug sensitivity of positive strains.Methods The PCR was applied to detect 8 subtypes of the mcr gene and the carbapenemase gene of the mcr-positive strain in 128 colistin-resistant strains isolated from fecal samples and 130 carbapenem-resistant strains isolated from clinically infected samples,and the sequence of positive amplification products was analyzed.The mcr-positive strains were identified by mass spectrometry and the drug sensitivity was analyzed.The plasmid transfer assay was performed to verify the transfer of mcr gene.PCR was used to type the plasmids and detect the presence of 12 virulence-related genes.Results No mcr2,mcr3,mcr4,mcr5,mcr6,mcr7,and mcr8 gene was found in 128 strains of colistin-resistance.None of the mcr2,mcr3,mcr4,mcr5,mcr6,mcr7,and mcr8 gene was found in 130 clinical samples of carbapenem-resistance.The mcr1-positive strain of carbapenem-resistance did not carry the carbapenemase gene,and its result of the antibiotic susceptibility test showed that it was intermediate to colistin.It was generally resistant to the drugs of sulfonamides,quinolones,carbon Penicillins,cephalosporins and so on.It also produced ESBLs.The mcr1-carrying isolate could transfer the mcr1 gene to the recipient strains successfully.6 types of incompatibility plasmids and 3 types of virulence-related genes were detected in mcr1-carrying isolates.Conclusion There is a certain prevalence of mcr1 in the gut bacteria-resistant strains and the clinical carbapenem-resistant strains,and the prevalence of the remaining 7 types of mcr gene is still low.This paper provides the clinical basis to study the relationship between the mcr gene with ESBLs and carbapenemase.