Mechanism of resistance of Pseudomonas aeruginosa to carbapenems / 上海第二医科大学学报

ABSTRACT

Objective To investigate the mechanism of resistance of clinical isolates of Pseudomonas aeruginosa to carbapenems.Methods Fifty-eight strains of imipenem-and meropenem-resistant Pseudomonas aeruginosa were isolated.Modified K-B technique was adopted in the susceptibility test by adding ?-lactamases inhibitors and efflux pumps inhibitors to M-H agar plates.The refined three-dimensional extract test was used to detect ?-lactamases.The genes of metallo-enzyme IMP,VIM,as well as outer membrane porin D2(OprD2) were analyzed with polymerase chain reaction.Results Among the 58 strains of carbapenems-resistant Pseudomonas aeruginosa,53 produced over-expressed active efflux and continuously produced large amont of AmpC enzyme,15 of which were accompanied by the loss of OprD2,and 1 of which were accompanied by extended spectrum ?-lactamases(ESBLs).Among the 5 strains which neither produced over-expressed active efflux nor ?-lactamases,only 1 was found with OprD2 gene deletion.Metallo-enzyme was not detected in any of the 58 strains.Conclusion The mechanism of resistance of Pseudomonas aeruginosa to carbapenems was mainly the production of the over-expressed active efflux combined with the continuous production of large amount of AmpC enzyme.Sixteen of the strains were accompanied by the loss of OprD2 gene.