mcr-1阳性类噬菌体质粒与F33:A-:B-质粒共整合形成的融合质粒的生物学特性分析

Biological Characteristics of Co-integrated Plasmid Derived from mcr-1-positive-phage-like Plasmid and F33∶A-∶B-Plasmid

为了分析猪源大肠杆菌中mcr-1阳性不可接合类噬菌体质粒pD72-mcr-1与bla CTX-M-55阳性可接合的F33∶A-∶B-质粒pD72-F33融合形成的共整合质粒pD72C的生物学特性,评估该融合质粒对mcr-1传播的潜在作用,本实验采用生长曲线测定、质粒稳定性实验、竞争性实验和接合实验,测定了融合质粒pD72C和亲本质粒pD72-F33对宿主菌的适应性、融合能力和扩散能力。结果表明:融合质粒pD72C在无抗生素的环境中能稳定传代9 d,对宿主菌有适应性优势,且比亲本质粒pD72-F33具有更好的竞争优势;该融合质粒表现出较高的融合频率和接合频率,说明该融合质粒能够扩展菌株的耐药谱并促进粘菌素耐药基因mcr-1的传播。

In order to analyze the biological characteristics of the cointegrated plasmid pD72C formed by the fusion of non-conjugative mcr-1-positive-phage-like plasmid pD72-mcr-1 and conjugative bla CTX-M-55 positive IncF33∶A-∶B-plasmid pD72-F33 and evaluate the potential role of the fusion plasmid in mcr-1 transmission,the growth curve test,plasmid stability test,competition experiment,conjugation assay were used to determinate the fitness,fusion and diffusion potentiality of the co-integrated pD72C and the parental plasmid pD72-F33.The results showed that the fusion plasmid remained stable for 9 days of passage in an antibiotic-free environment,presented a adaptive advantage for its host,and showed higher fitness than the parental plasmid pD72-F33.Moreover,the fusion plasmid exhibited the relatively high fusion frequency and conjugation frequency.Fusion plasmids can expand the drug resistance spectrum of strains and promote the transmission of drug resistance gene mcr-1.