Phenotypic and genotypic investigation of metallo-β-lactamases in Pseudomonas aeruginosa clinical isolates in Bushehr, Iran

Objective(s): Production of metallo-β-lactamases (MBLs) is an important mechanism of resistance to carbapenems. This study aimed to detect the MBL-producing Pseudomonas aeruginosa clinical isolates and to investigate the presence of blaVIM, blaIMP, blaSPM, blaNDM, blaGIM, blaAIM, and blaSIM genes in these isolates in Bushehr, Iran. Materials and Methods: A total of 169 P. aeruginosa clinical isolates were collected from three hospitals in Bushehr. The modified carbapenem inactivation method (mCIM) was used for the phenotypic detection of carbapenemase production. A combination disk test (CDT) was performed for the phenotypic detection of MBL production. To investigate the presence of blaVIM, blaIMP, blaSPM, blaNDM, blaGIM, blaAIM, and blaSIM genes, PCR and sequencing was carried out. Results: Based on the results of mCIM, 40 (23.7%) of 169 isolates were carbapenemase producers. CDT revealed that 26 (15.4%) isolates were MBL producers. blaIMP, blaNDM, and blaVIM genes were found in 18 (69.2%), 8 (30.8%), and 1 (3.8%) of the MBL-producing isolates, respectively. Coexistence of blaIMP and blaNDM was observed in 2 (7.7%) MBL-producing isolates. Among all 169 P. aeruginosa isolates, 23 (13.6%) harbored blaNDM, 18 (10.6%) carried blaIMP, and 1 (0.6%) carried the blaVIM gene. blaSPM, blaGIM, blaAIM, and blaSIM were not found in the present study. Conclusion: blaNDM, blaIMP, and blaVIM genes were detected in this study, which could be a warning sign about the prevalence of these genes among P. aeruginosa clinical isolates in our region. Proper monitoring and detection of MBL-producing isolates are essential steps to prevent the spread of these isolates.