Investigation On Metallo-β-lactamase In Clinical Isolates Of Pseudomonas Aeruginosa

Pseudomonas aeruginosa is innate resistance to most commonly employed antimicrobial agents. The mechanism of multi-drug resistance of Pseudomonas aeruginosa was complex from exogenous DNA sources(e.g. plasmid, transposons, integron). As recent years, Pseudomonas aeruginosa resistance has continually risen to third generation cephalosporins, ceftazidime and imipenem. The Clinical and Laboratory Standards Institute (CLSI) is still non-existent standardized detection methodologies for metallo-β-lactamase(MBL).Objective: To investigate occurrence of MBL in clinical isolates of Pseudomonas aeruginosa for exploring and establishing a method for screening MBL in clinical microbiology laboratory and molecular epidemiology homogeneous in imipenem and ceftazidime resistant Pseudomonas aeruginosa for the reasonable selection of antibiotics.Methods: Pseudomonas aeruginosa strains isolated from Yantai and Zibo during Jan 2004 to Nov 2006 were collected and identified by ATB Expression ID32GN system. The test strains were screened by K-B method with imipenem and ceftazidime. The phenotype of Metallo-β-lactamase was screened by EDTA-IPM/ CAZ disk diffusion method and The E-test method. Molecular screening for blaIMP-1,blaVIM-2 was carried out using primers targeting the conserved regions of the MBL genes. Molecular genotype was by ERIC-PCR of imipenem and ceftazidime resistant Pseudomonas aeruginosa. The antimicrobial susceptibility for detecting MBL producer in Pseudomonas aeruginosa isolates to 8 antibiotics was tested by the minimal inhibitory concentrations (MIC) method, those antibiotics include imipenme, ceftazidime, amikacin, aztreonam, levofloxacin, gentamicin, cefoperazone, ciprofoxacin.Results: 302 strains of Pseudomonas aeruginosa isolated were collected. Among 34 test strains, 15 were positive in EDTA-IPM/CAZ disk diffusion method, 11 were positive in E-test method, 3 of the strains were found to produce IMP-1 and 5 of the strains were found to produce VIM-2. The strains produced Metallo-β-lactamase were multidrug resistance, the strains with positive in PCR method highly resistant. The antimicrobial susceptibility of isolates to 8 antibiotics was tested by MIC method for susceptibility of isolates to amikacin(60.0%) and ciprofloxacin (33.3%). 7 Molecular genotypes were by ERIC-PCR of 34 test strains.Conclusion: (1) In Pseudomonas aeruginose isolates indicated the emergence of MBL. (2) The disk diffusion test using EDTA-IPM/CAZ, E-test and PCR are convenient and credible method for detecting MBL Producer in clinical microbiology laboratory. (3) ERIC-PCR will be helpful for cognate in test strains nosocomial infections. It is very important to monitor the production of MBL and typing of ERIC-PCR for Pseudomonas aeruginosa strains .