Detection of vim- and ipm-type metallo-beta-lactamases in Pseudomonas aeruginosa clinical isolates

BACKGROUND: Pseudomonas aeruginosa is the most important bacterium isolated from burn wounds, and its resistance to imipenem due to metallo-beta-lactamases is increasing. This study was designed to detect vim1, vim2, ipm1 and ipm2 metallo-beta-lactamases genes between Pseudomonas aeruginosa isolates isolated from Shahid Motahari Burns Hospital, Iran. METHODS: To that end, we isolated 483 nonduplicate consecutive isolates of P. aeruginosa from burn infections; and after biochemical confirmation, we examined the imipenem susceptibility via the Kirby-Bauer method. All the imipenem-resistant and imipenem-intermediate isolates were screened for vim1, vim2, ipm1 and ipm2 genes through the PCR method. RESULTS: From the 483 isolates, 272 (56) and 63 (13) isolates had resistant and intermediate zones in their imipenem antibiogram pattern, respectively. Fifty-four (16.1), 7 (2.1), 22 (6.6), and 11 (3.3) of the resistant and intermediate isolates had vim1, vim2, ipm1 and ipm2 genes in their PCR results, respectively. CONCLUSION: MBL-mediated imipenem resistance in P. aeruginosa is a cause for concern in the treatment of infective burn patients. The rate of imipenem resistance due to MBL was increased dramatically and newer versions of MBL families were detected for the first time. These results suggest that an effective method should be provided to fight MBL production in clinical isolates