isolation of pseudomonas aeruginosastrains producing metallo beta lactamases from infections in burned patients and identification of blaimp and blavimgenes by pcr

background & objectives: pseudomonas aeruginosais one of the most important causes of nosocomial infections particularly in immunodeficient patients. several antibiotics such as betalactams, aminoglycosides and quinolones are used for the treatment of infections caused by this organism, but the prevalence of multidrug resistant strains has been reported frequently. beta lactamase production is one of the most important resistant factors. metallo-beta-lactamase (mbls) have a broad-substrate spectrum, they hydrolyse  all beta-lactams except for the monobsctam aztreonam. in this study, the metallo-beta-lactamase production in pseudomonas aeruginosastrains were investigated. material and methods: initially, the antibiotic resistance pattern of 100 clinical strains isolated from infections in burned patients in ahwaz taleghani hospital was determined by disc diffusion method. all the clinical pseudomonas aeruginosaisolates nonsusceptible to imipenem were screened for production of  mbls by etest with imipenem/ imipenem plus edta (etest mbl).dna was extracted from colonies by  simple boiling method. the extracted dnas were then examined by pcr involving specific primers for blavim and blaimp mbl genes. results: based on the obtained results, the percentage of resistance was as below: cefepime100%,  ceftazidime81%, ticarcillin70%, imipenem41%, meropenem23% and piperacillin20%. the investigation for mbl production in the strains resistant to ipm by etest mbl showed that 8 out of 41(19/51%) imipenem resistant isolates were mbl producers. all the clinical  p. aeruginosaisolates that were  nonsusceptible to ipm were then examined by pcr for the presence of the blavim and bla imp genes. of  the 41 p.aeruginosastrains isolated during the study period, 8(19/51%) were positive for blavim gene.the results from pcr assay represented thet 8 isolates among 41 ipm resistant strains of pseudomonas aeruginosa were positive for blavim gene. the remaining 33(80/49%) were negative for vim and imp mbls. conclusion:the results of this investigation in agreement with shows that, the antibiotic resistance of pseudomonas aeruginosais increasing in burn hospitals and the mbls production can be the cause of this issue.