耐药质粒在肠道杆菌间的接合传递研究

The Conjugational Transfer of R Plasmids in Enteric Bacilli

选用１３ 种抗菌药物对１８ 株肠道杆菌进行药敏试验、质粒检测并用传统及改良两种接合转移试验方法，以５ 株伤寒杆菌的不相容性 Ｃ群（ Ｉｎｃ Ｃ） Ｒ 质粒、６ 株大肠杆菌及２ 株鼠伤寒杆菌的 Ｒ 质粒作供体，研究其在肠道杆菌间的传递。结果显示， Ｒ 质粒能在４ 种肠道杆菌间互相传递，其中伤寒杆菌 Ｉｎｃ Ｃ 群 Ｒ 质粒能在这４ 种菌中稳定复制并表达耐药性。质粒的可传递性给阻断耐药性的传播和疾病的防治带来很大困难，单纯消除某个菌中的耐药质粒已难以奏效，正常菌群中庞大的耐药基因库是致病性耐药菌株流行的潜在危险；合理选择、控制抗生素的使用，降低“选择性压力”显得尤为重要。

The frequency of antimicrobial resistance among 18 strains of enteric bacilli was studied. All strains were tested against 13 different antimicrobial agents by means of Kirby-Bauer disc agar diffusion on Mueller-Hinton media. The plasmid profiles were also determined. In the conjugation test, strains harbouring R plasmids were tested for the ability to transfer their R plasmids to a plasmid free laboratory strain of E. coli K 12 W 1485 Rif r. Thereafter, E. coliK 12 W 1485 Rif r receiving R plasmids of enteric bacilli were used as donors, while the sensitive and resistant strains of S. typhi, S. typhimurium and S. flexneri as recipients. The R plasmids could transfer among E coli, S. typhi, S. typhimurium and S. flexneri and the IncC plasmid of S. typhi could replicate and express antimicrobial resistance steadily in the four spicies of different enteric bacilli. R plasmids can be easily transfered from pathogenic enteric bacilli to E. coli and then to other sensitive and resistant pathogenic bacilli. It is very difficult to block and prevent the spreding of antimicrobial resistance. More attention should be paied to reduce the “selecting pressure”.