Antibiotic Resistance Of Imipenem In Clinical Isolated Pseudomonas Aeruginosa

ObjectiveTo investigate metallo-beta-lactamase and postantibiotic effect of imipenem on Pseudomonas aeruginosa in our hospital. Providing the laboratory evidence for guiding antibiotic therapy and controlling nosocomial infections.MethodsBacterial identification and antibiotic susceptibility tests (MICs) were performed by VITEK 2 Compact system from clinical departments'isolates from July 2007 to October 2008. MBL were screened by double-disk synergy test and amplified by PCR for Pseudomonas aeruginosa isolates which were nonsensitive to imipenem, then the amplified blaVIM-2 gene were sequenced and identified. Colony count method and flow cytomtry were used to test the postantibiotic effect of imipenem on Pseudomonas aeruginosa which were sensitive to imipenem.Results1. The isolated rate of Pseudomonas aeruginosa was 9.2%(335/3653). Most Pseudomonas aeruginosa strains were isolated from ICU ward. 80.6% Pseudomonas aeruginosa were isolated from respiratory tract.2. The strains which were nonsensitive to imipenem were more resistant to aztreonam, ceftazidime, ciprofloxacin, levofloxacin, and piperacillin/tazobactam than the sensitive isolates. (P<0.05)3. VIM-2 metallo-beta-lactamase-producing Pseudomonas aeruginosa strains were detected in our hospital. The positive rate is 6.8%(3/44).4. Sulfhydryl-compound-imipenem double-disk synergy test is more sensitive than EDTA- imipenem double-disk synergy test in screening MBL on Pseudomonas aeruginosa strains.5. Postantibiotic effect of imipemen on Pseudomonas aeruginosa is 0.14h in twice MIC, 1.21h in four times MIC, 2.42h in eight times MIC, 2.66h in ten times MIC. 6. The PI% value of Pseudomonas aeruginosa during the period of postantibiotic effect is higher than the viable bacteria and lower than the dead bacteria by flow cytometry.Conclusions1. Pseudomonas aeruginosa strains were prevalent in ICU and most of the strains were multi-resistant to antibiotics, we shuould monitor the resistance of bacteria, and use antibiotics reasonably.2. Producing metallo-beta-lactamase is a main resistant mechanism of Pseudomonas aeruginosa which is nonsensitive to imipenem.3. Sulfhydryl-compound-imipenem double-disk synergy test is more convenient, it can be recommended on clinical laboratory daily work.4. The more concentration imipenem is, the longer PAE on Pseudomonas aeruginosa presents.5. Flow cytometry is a new and convenient method to determin PAE.