ABSTRACT
Objective To investigate if the 23 strains of highly-resistant P.aeruginosa isolated from different patients in the in- tensive care unit (ICU) have the same origin;and explore the related mechanisms of carbapenem resistance in these multidrug- resistant P.aeruginosa.MethOds Antimicrobial susceptibility testing was performed using disk-diffusion technique.The strains were genotyped by rep-PCR with the primer ERIC2 followed by electrophoresis in agarose gel.We used a previously described imipenem-EDTA double-disk test for screening MBL-producing P.aeruginosa.Polymerase chain reaction for amplification of blaOprD, blaIMP, and bla VIM were performed to detect corresponding mutants.Results The result of antimicrobial suscepti- bility testing showed that 20 of the 23 P.aeruginosa isolates were muhidrug-resistant and highly resistant to imipenem and meropenem, and at least 5 antimicrobial agents tested in this study.The analysis of the rep-PCR products indicated that all the 19 carbapenem-resistant strains had an identical band pattern, which was different from that seen in the sensitive strains.Al- though imipenem-EDTA double-disk test identified 5 MBL-producing strains, PCR found that all the 23 strains were negative for bla VIM and blaIMP.Only one OprD-deficient mutant was identified.Conclusions The 19 highly-resistant strains of P. aeruginosa derive from a common origin.More researches are needed to clarify their mechanism of carbapenem resistance.