Imipenem-resistant Pseudomonas aeruginosa and Detection of Metallo-β-lactamase in an Intensive Care Unit

OBJECTIVE To evaluate the spectrum of imipenem-resistant Pseudomnas aeruginosa and the production of metallo-β-lactamase.METHODS The clinical strains of P.aeruginosa were collected from Jan to Dec 2007.The results of antimicrobial susceptibility tests and detection of metallo-β-lactamase were analyzed.Antimicrobial susceptibility tests were performed by K-B methods;the production of metallo-β-lactamase was tested by CAZ-EDTA synergy method.RESULTS Sixty strains were isolated,imipenem-sensitive and resistant strains were 40(66.7%) and 20(33.3%),respectively,and 7 strains with metallo-β-lactamase were detected.Among imipenem-resistant strains,at least 90.0% strains were resistant to meropenem,gentamicin,tobramycin,ciprofloxacin and SMZ-TMP;at least 80.0% strains were resistant to piperacillin and piperacillin/tazobactam;50.0% strains were resistant to ceftazidime and cefepime;polymyxin E was less resistant than others.Twenty strains were resistant to at least 3 antimicrobial agents,which was obviously higher than 27.5% of imipenem-resistant strains.CONCLUSIONS The resistance rate of imipenem-resistant P.aeruginosa is higher than imipenem-sensitive ones.The production of metallo-β-lactamase is one of the mechanisms of P.aeruginosa resistance to imipenem and shou1d be detected carefully,which could help us medicate reasonably in clinic and avoid using medicine which could induce and strengthen the resistance.