Study on antimicrobial resistance characteristics and mechanism of imipenem-resistant Pseudomonas aeruginosa

Objective To investigate the antimicrobial resistance characteristics and the mechanisms of imipenem-resistance of Pseudomonas aeruginosa producing carbapenemase.Methods Sixty five strains from patients were identified and drug susceptibility test was performed by Micro-Walkaway-40 automatic microbial analysis system.The susceptibility of cefoperazone/sulbactam was performed by KB method.The resistant genes of Pseudomonas aeruginosa isolates,including IMP,VIM,GIM,SM,GS,OXA and oprD2,were detected by PCR.The influence of active efflux inhibitors carbonyl cyanide chlorophenylhydrazone(CCCP) on minimal inhibitory concentration(MIC) of both standard Pseudomonas aeruginosa and Imipenem-resistant Pseudomonas aeruginosa to ciprofloxacin,enrofloxacin and tetracycline were measured by agar dilution method.Results The resistance rate of imipenem-resistance Pseudomonas aeruginosa isolates to cefoperazone sulbactam(Sulperazone),piperacillinl tazobactam(Tazocin),amikacin,ceftazidime,cefepime(Maxipime) and ciprofloxacin was 38.5%,43.1%,44.6%,50.8%,53.8% and 55.4%,respectively.Out of sixty five strains,11were positive for IMP gene(16.9%),4 for VIM(6.2%),5 for oprD2(7.7%).CCCP had distinct effect on resistance strains MIC to ciprofloxacin and enrofloxacin,and seven strains were positive(10.8%).Conclusion The P.aeruginosa isolates with imipenem-resistance shows seriou multidrug-resistance.It was the major antimicrobial merchanisms that the metallo-beta-lactamase producing of IMP,efflux pump and loss of oprD2 gene led to PA resistant to cephalosporins and carbapenems in Jiaodong district.