Périchon Bruno, Courvalin Patrice, Galimand Marc
Unité des Agents Antibactériens, Institut Pasteur, 75724 Paris Cedex 15, France.
Antimicrob Agents Chemother. 2007 Jul;51(7):2464-9. doi: 10.1128/AAC.00143-07. Epub 2007 Apr 30.
Plasmid pIP1206 was detected in Escherichia coli strain 1540 during the screening of clinical isolates of Enterobacteriaceae for high-level resistance to aminoglycosides. The sequence of this IncFI conjugative plasmid of ca. 100 kb was partially determined. pIP1206 carried the rmtB gene for a ribosome methyltransferase that was shown to modify the N7 position of nucleotide G1405, located in the A site of 16S rRNA. It also contained the qepA (quinolone efflux pump) gene that encodes a 14-transmembrane-segment putative efflux pump belonging to the major facilitator superfamily of proton-dependent transporters. Disruption of membrane proton potential by the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone in a transconjugant harboring the qepA gene resulted in elevation of norfloxacin accumulation. The transporter conferred resistance to the hydrophilic quinolones norfloxacin and ciprofloxacin.
在对肠杆菌科临床分离株进行高水平耐氨基糖苷类筛选过程中，在大肠杆菌菌株1540中检测到质粒pIP1206。对这个约100 kb的IncFI接合性质粒的序列进行了部分测定。pIP1206携带核糖体甲基转移酶的rmtB基因，该酶可对位于16S rRNA A位点的核苷酸G1405的N7位置进行修饰。它还包含qepA（喹诺酮外排泵）基因，该基因编码一种属于质子依赖性转运蛋白主要易化子超家族的14跨膜段推定外排泵。在携带qepA基因的接合子中，外排泵抑制剂羰基氰化物间氯苯腙对膜质子电位的破坏导致诺氟沙星积累增加。该转运蛋白赋予对亲水性喹诺酮类药物诺氟沙星和环丙沙星的抗性。
