Contributions of different quinolone resistance mechanisms in Escherichia coli / 中华微生物学和免疫学杂志

ABSTRACT

Objective To characterize the roles of different quinolone resistance mechanisms in quinolone-resistant Escherichia coli isolates,including different topoisomerase point mutations,efflux pumps and outer membrane proteins.Methotis Through homologous gene recombination methods,different quinolone-resistant mechanisms of E. coli mutants were constructed and the susceptibility changes of these mutants to different antimicrobials were measured.Resuits Efflux pumps AcrAB and outer membrane protein TolC played different roles in different E. coli isolates.Compared with other mechanisms,the mutations in topoisomerases played a dominant role in quinolone resistance.Only the mutations jn parC had no effect on quinolone resistance,which further confirmed parC was the secondary target of quinolones in E.coli.Fluoroquinolone susceptible E.coli would automatically become highly resistant to quinolones after acquiring the point mutations in both gyrA(S83L,D87N)and parC(S80I,A108V),but not requiring the over-expres-sion of efflux.Conclusion The mutations in topoisomerases play a dominant role in E.coli quinolone resistance,and the mutations in both gyrA and parC are required.