Plasmid-mediated quinolone resistance.
The first plasmid-mediated gene involved in quinolone resistance (qnrA1) was reported in 1998. It codes for a pentapeptide-repeat protein that protects type II topoisomerases from quinolones. Additional related plasmid-mediated genes (qnrB, qnrS and qnrC) and chromosomal homologs of them have also been discovered. Two other plasmid-mediated resistance mechanisms were later reported: modification of quinolones with a piperazinyl substituent by the acetyltransferase Aac(6)-Ib-cr and active efflux by QepA, a pump related to the major facilitator superfamily transporters. These genes have a wide geographical distribution (essentially in enterobacteria), although their real prevalence is only partially known because of the difficulty of phenotypic detection of this type of resistance. Although these mechanism cause low-level resistance, they favor and complement the selection of additional mechanisms of resistance.
Service of Microbiology, University Hospital Marqués de Valdecilla, and Department of Molecular Biology, University of Cantabria, Santander, Spain. lmartinez@humv.es
Luis
L
Martínez-Martínez
María
M
Eliecer Cano
José
J
Manuel Rodríguez-Martínez
Jorge
J
Calvo
Alvaro
A
Pascual
D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000187:drug effects / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D010957:Plasmids / Q000235:genetics*; D015363:Quinolones / Q000494:pharmacology* / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones