Analysis of antimicrobial resistance and metallo-β-lactamase genes in Pseudmonas aeruginosa isolates

Objective The aim of this study was to investigate the antimicrobial susceptibility and the prevalence of metallo-β- lactamases (MBLs) in clinical isolates of P. aeruginosa. Methods A total of 200 nonduplicate clinical isolates of P. aeruginosa were collected from November 15, 2010 to April 15, 2011 in Xiangya Hospital, Central South University. The antimicrobial susceptibility was tested by VITEK-2 automated microbial analysis system. The isolates positive in double disk synergy test were selected for PCR to identify blaIMP, blaVIM, blaSPM and blaNDM genes and sequencing analysis. The positive strains then underwent examination for class I integrons by PCR with primers specific to class I integrase (IntI1). Results The P. aeruginosa strains were primarily isolated from ICU, accounting for 27.5%. Antimicrobial susceptibility testing showed that the rate of resistance to meropenem was the lowest (8.5%), and to gentamycin was the highest (38.5%). Six (3.0%) isolates harbored MBLs and 2 isolates were demonstrated by PCR. Sequence analysis revealed the presence of blaIMP-1 genes. VIM, SPM, and NDM-type metal enzymes were not identified. The strains positive in phenotypic test were all positive for blaIntIl. Conclusions IMP-1 is the most prevalent genotype of metallo-β-lactamase in this collection of isolates. The prevalence of metallo-β-lactamase-producing P. aeruginosa is low in this hospital. The overall resistance of P. aeruginosa is serious, but they are relatively susceptible to carbapenems.