Current Resistance Status And Genotypes Of Imipenem-resistant Pseudomonas Aeruginosa

Objective 1) To investigate the drug resistance of Imipenem-resistant Pseudomonas aeruginosa to instruct clinical application of antibiotics. 2) To establish a convenient polymerase chain reaction(PCR)method for bacterial DNA fingerprints analysis in epidemiology research of Imipenem-resistant Pseudomonas aeruginosa. 3) To explore and establish a simple and convenient method for screening metallo- β-lactamase-producing Pseudomonas aeruginosa in the clinical microbe laboratory. 4) To investigate the genotype characteristics and antibiotics sensitivity of clinical Pseudomonas asaeruginosa isolates producing metallo-B -lactamase.Methods 1) Imipenem-resistant Pseudomonas aeruginosa isolated from 2001 to 2002 were identified by VITEK 32 system. The minimal inhibitory concentrations (MlC)of them to 10 antibiotics, including Imipenem, Piperacillin, Cefotaxime, Ceftazidime, Cefepime, Aztreonam, Ciprofloxacin, Gentamycin, Amikacin and Chloromycetine were detected by agar dilution method. 2) Strains were typed by rep-PCR with the primer enterobacter repetitive intergenic consensus(ERIC) following electrophoresis in agarose gel. 3) Using substrate Ceftazidime, Cefotaxime and Imipenem, enzyme inhibitor EDTA Na2 and 2-mercaptopropionic acid, the microbe sensitivity synergic tests were processed by KB method in MH agar. 4) Metallo-β-lactamase gene was detected by PCR method using primers specific for blaIMP-1, blaIMP-2, blaVIM-1 and blaVIM-2, respectively, and the PCR products were purified and sequenced.Results 1) Among 398 strains of Pseudomonas aeruginosa, 56 of them were resistant to Imipenem, mainly isolated from ICU ward. The resistance rate to Chloromycetine was the highest(85.7%). The resistance rates to Cefepine, Aztreonam and Amikacin were 33.9%, 32.1% and 35.7%, respectively. The resistance rates toother 6 antimicrobial agents were from 50.0% to 70.0%. 2) 56 Imipenem-resitant Pseudomonas aeruginosa strains were typed to 33 genotype by ERIC-PCR. 3) 5 metallo-β-lactamase-producing Pseudomonas aeruginosa were detected among 56 strains. 4) Amplification of blaVIM-2 gene was positive in those 5 strains, and negtive in other strains. All 5 strains were resistant to most β-lactams antibiotics. Only was it rather sensitive to Aztreonam and Amikacin.Conclusion 1) Pseudomonas aeruginosa strains resisted to Imipenem remains a problem. And they show increasing tendency year by year. 2) The method of ERIC-PCR is practical and economical for epidemiology research in nosocomial infection. 3) The synergic test was simple, convenient and sensitive for screening metallo- β-lactamase-producing bacteria. It was suitable for screening metallo-β-lactamase- producing Pseudomonas aeruginosa routinely in the clinical microbe laboratory. 4) VIM-2 was the genotype of metallo-β-lactamases in clinical isolates of Pseudomonas aeruginosa in this research. Multiple drugs resistant occurred seriously in these strains.