环境放线菌中的达托霉素抗性机制

Characterization of daptomycin-resistance in environmental actinomycetes

【目的】研究环境放线菌中的达托霉素抗性机制,为临床耐药机制的出现提供预警。【方法】通过测定土壤放线菌(49株)和药用植物内生放线菌(10株)的达托霉素耐受谱,筛选达托霉素抗性菌株;通过达托霉素灭活实验,确定抗性菌株的灭活能力;通过形态观察和16S rRNA序列分析分类鉴定达托霉素降解菌。通过PCR扩增检测达托霉素去酰基化酶基因在降解菌株中的分布情况。【结果】本研究中所有的环境放线菌均耐受达托霉素。在土壤放线菌中和药物植物内生放线菌中,分别有24株(49.0%)和4株(40%)能够灭活达托霉素,25(51.0%)株和6株(60%)通过其他机制耐受达托霉素。序列测定表明,链霉菌属(Streptomyces)、小单孢菌属(Mcromonospora)和诺卡氏菌属(Nocardia)的部分菌株有灭活达托霉素的能力。PCR扩增表明,5株(17.9%)放线菌含有编码达托霉素去酰基酶的基因。【结论】环境放线菌具有超高的达托霉素抗性频率,灭活达托霉素是主要抗性机制之一。

[Objective] Daptomycin-resistance in environmental actinomycetes was studied to provide warning systems for emerging clinical resistance.[Methods] In total 49 soil and 10 endophytic acitnomycetes were used in this study.The daptomycin resistant strains were identified by measuring daptomycin resistance profile.Subsequently,daptomycin inactivating assay was preformed to distinguish resistance from other nondestructive mechanisms.Then,the strains of interest were determined by morphology and 16S rRNA gene sequence analysis.Finally,PCR analysis was used to detect the daptomycin acylase gene（dpa） encoding daptomycin acylase in those strains [Results] All strains tested in this study were resistant towards daptomycin.Of them 24 soil acitnomycetes and 4 endophytic actinomycetes had the ability to inactivate daptomycin,while the remaining strains used other measures to confer resistance.Sequence analysis demonstrated that strains inactivating daptomycin were Streptomyces,Micromonospora and Norcadia.PCR analysis shows that 17.9% strains contained the dpa.[Conclusion] There is very high percentage of resistance in environmental actinomycetes and inactivating daptomycin is one of the main resistant mechanisms.