碳青霉烯耐药基因院外流行及不同抗菌机理的抗菌药物对其传播的影响

Prevalence of out-of-hospital prevalence of carbapenem-resistance genes and influences of antibiotics with different antibacterial mechanisms on the genes spread

目的分析院外泌尿系统耐碳青霉烯类抗菌药物的菌株分布及耐药基因传播方式,进一步探讨不同抗菌机理的抗菌药物对耐药质粒接合转移的影响。方法在991份体检健康者非重复尿液标本中筛查亚胺培南耐药菌株,确定碳青霉烯耐药基因型。采用多位点序列分型(MLST)对主要耐碳青霉烯菌株进行分型,确定不同ST之间的系统发育关系,揭示院外耐药基因的传播方式;接合实验分析不同亚抑菌浓度氨苄西林、环丙沙星、庆大霉素处理供体菌和/或受体菌不同时间对耐药质粒接合效率的影响。结果共检出18株院外健康人群的非重复耐碳青霉烯菌株(1.82%,18/991),主要为大肠埃希菌(E.coli)(44.44%,8/18),主要基因型为blaKPC-2(7/8);MLST结果表明,7株E.coli分别属于ST-10、ST-101、ST-131、ST-405、ST-410、ST-1193和ST-2562;同源聚类分析表明,7株E.coli类型具有较高的多样性;接合效率范围为(1.59±0.20)×10-4~(4.01±1.31)×10-4;接合效率最高供体菌经1/8 MIC抗菌药物处理9 h的条件下,其接合效率较无抗菌药物处理组增加最明显;3种不同作用机理的抗菌药物均可提高接合效率,而氨苄西林提高最明显。结论本研究中耐碳青霉烯大肠埃希菌(CREC)基因型主要为blaKPC-2,传播方式以水平传播为主;亚抑菌浓度抗菌药物可以促进该耐药质粒的接合转移,不同作用机理的抗菌药物及不同抗菌药物胁迫条件对接合效率的影响具有显著差异。

Objective To analyze the distribution of carbapenem-resistant strains and the transmission mode of resistance genes in the bacteria strains from urinary system of the individuals outside hospitals,and further explore the impacts of the antibiotics with different antibacterial mechanisms on the conjugation transfer of resistant plasmids.Methods The imipenem-resistant strains from 991 non-repetitive urine samples of healthy individuals were screened for determining the carbapenem-resistance genotypes.Using the multilocus sequence typing(MLST)method,the main carbapenem-resistant strains were classified to determine the phylogenetic relationship between different sequence types(STs)and reveal the transmission mode of resistance genes in the individuals outside hospitals.The conjugation experiment was used to analyze the effects of different sub-inhibitory concentrations of ampicillin,ciprofloxacin,and gentamicin on the conjugation efficiency of resistant plasmids in the bacteria of donor and/or recipient at different times.Results A total of 18 non-repetitive carbapenem-resistant strains(1.82%,18/991)were detected in healthy individuals outside hospitals,among which Escherichia coli(E.coli)(44.44%,8/18)was the main strain with main genotype being bla_(KPC-2)(7/8).MLST showed that the 7 strains of E.coli with bla_(KPC-2)genotype belonged to ST-10,ST-101,ST-131,ST-405,ST-410,ST-1193,and ST-2562,respectively.Homologous clustering analysis showed that the type of the 7 E.coli strains exhibited high diversity.The range of joint efficiency was(1.59±0.20)×10~(-4)to(4.01±1.31)×10~(-4).The highest conjugation efficiency was observed in the donor bacteria treated with 1/8 of MIC of antibiotics for 9 hours,and the conjugation efficiency most significantly increased compared to the group without antibiotic treatment.Three antibiotics with different mechanisms of action could all improve conjugation efficiency,among which ampicillin exhibited the most significant improvement.Conclusion In this study,the genotype of carbapenem-resistant Escherichia coli(CREC)was mainly bla_(KPC-2)with a main mode of horizontal transmission.Antibiotics with sub-inhibitory concentrations could promote the conjugation transfer of the resistant plasmid.There may be significant differences in the effects of antibiotics with different mechanisms of action and different antibiotic stress conditions on the conjugation efficiency.