Imipenem-resistant Pseudomonas aeruginosa strains carry vim-type metallo-beta-lactamases isolated from intensive care unit, Shahid Beheshti Hospital, North of Iran

Background: Pseudomonas aeruginosa is the causing agent of many hospital infections and metallo-beta-lactamases (MBL) are being reported with increasing frequency. The aim of this study was to determine the frequency of metallo-β-lactamases (MBL) and VIM-1 gene in multidrug-resistant strains of P. aeruginosa isolates and to compare the methods of phenotypic and molecular detection. Materials and Methods: In 2011- 2012, 50 samples of non – duplicate P. aeruginosa were isolated from intensive care units and tested for MBL production using phenotypic methods. Minimal Inhibitory concentrations (MICs) were determined by commercial micro dilution panels. The presence of metallo-β-lactamase (MBL) genes was established by polymerase chain reaction (PCR) with specific primers targeting the bla (VIM) genes. Results: We used 50 clinical isolates amongst which 18 (%36) were found resistant to imipenem. Productions of MBL were detected in 15 (30%) isolates applying phenotypic method. PCR assay showed that 9 (18%) isolates carried aVIM-1 gene. MBL- producing strains were shown 100% resistant to cefepime, ceftazidime, ceftriaxone, cefotaxime and imipenem. Amikacin and ofloxacin appeared to be the most active antimicrobial agent. Conclusion: These findings demonstrate the emergence of bla (VIM-1) producing P. aeruginosa in North of Iran. VIM metallo-beta-lactamases producing P. aeruginosa strains can cause serious infections that are difficult to treat, therefore, there is a need for rapid identification and the timely implementation of infection control measures in combination with systematic surveillance to monitor its potential clonal spread.