Biological Journal of Microorganism (Jun 2015)
Detection of blaSPM-1 metallo-β-lactamase gene in Imipenem-resistant Pseudomonas aeruginosa strains isolated from hospitalized patients in Isfahan hospitals
Abstract
Introduction: Pseudomonas aeruginosa is an opportunistic human pathogen which causes serious problems especially in people who have immunodeficiency. Recently, metallo-β-lactamase (MBLs) resistance in this bacterium has led some difficulties in treating bacterial infections. MBL gene family, including blaSPM-1 caused resistance to beta-lactam antibiotics especially carbapenem (eg, imipenem) and have been reported with high prevalence worldwide. The aim of this study is detection of metallo-β-lactamase gene blaSPM-1 in Imipenem-resistant Pseudomonas aeruginosa strains isolated from hospitalized patients in Isfahan hospitals. Materials and methods: In this study, 252 samples were isolated from various nosocomial infections. These isolates were identified as Pseudomonas aeruginosa by using biochemical tests. Disk diffusion method (Kirby-Bauer) was used to determine the bacterial drug resistance pattern. All imipenem-resistant isolates were screened for the presence of MBLs by using the Combine disk (IMP-EDTA). The minimal inhibitory concentration (MIC) of imipenem was determined by E-test on Mueller-Hinton agar. To detect blaSPM-1 gene, the isolates were subjected to polymerase chain reaction (PCR). Results: In total, 106 isolates of Pseudomonas aeruginosa were collected. Of all isolates, 62 (58.5 %) were found to be imipenem-resistant Pseudomonas aeruginosa. MIC levels in all strains of imipenem-resistant were MIC≥32μg/ml. Twenty-six (48 %) of imipenem-resistant Pseudomonas aeruginosa isolates were MBL positive. None of the isolates carried blaSPM-1 gene by PCR assay. Discussion and conclusion: Results of this study demonstrate that the rate of imipenem resistance due to MBL is increased dramatically. Early detection and infection-control practices are the best antimicrobial strategies for this organism. None of MBL-producing isolates in this study carry blaSPM-1 gene; therefore another gene in MBLs family should be investigated.
