[Detection of blaIMP and blaVIM metallo-beta-lactamases genes in pseudomonas aeruginosa strains isolated from wound of burnt patients in Tehran Shahid Motahari hospital during 2011, Iran]

During recent years, metallo-beta-lactamase [MBLs] producing Pseudomonas aeruginosa has been reported as an important cause of nosocomial infection. Also, infection with this bacterium has increased rate of mortality and health care costs. The aim of this study was to determine the antibiotic resistance pattern and to detect blaVIM and blaIMP Metallo-beta-lactamase genes in P. aeruginosa isolated from patients hospitalized in the burn ward. This descriptive study was conducted on P. aeruginosa strains isolated from patients hospitalized in the burn ward of Tehran Shahid Motahari Hospital between September and January 2011. For all MBL-producing strains, antibiotic resistance pattern was determined by disc diffusion method according to CLSI guidelines. CDDT method was used for detection of MBL [imipenem-imipenem+EDTA], and PCR and sequencing techniques were used to detect MBL genes, blaVIM and blaIMP. Eighty-three percent of 100 P. aeruginosa isolates were resistant to imipenem. Using combination disk diffusion test [CDDT] method, 48 isolates were detected to have MBL, of which 6 isolates were positive for blaIMP-1 gene, and all of them did not have blaVIM gene. Also, 4 [8.3%] patients with MBL-producing P. aeruginosa infection died in the hospital. The results of this study revealed that high percentage of P. aeruginosa strains are MBL-producer. Therefore, detection of MBL-producing strains is essential for better control and treatment of burnt patients

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

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. 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 FOR method. 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. 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