RESUMEN
This study was carried out to evaluate the existence of the TEM, SHY and PER ESBL genes in ESBL producing strains of Pseudomonas aeruginosa isolated from burnt patients at Shafa-hospital, Kennan, Iran. A total of 120 strains of P. aeruginosa were isolated from 245 patients in burn unit of Shafa-hospital during January 2006 to December 2007. MIC of antibiotics was measured using agar dilution test ESBL producing strains were detected by double-disc synergy method containing amoxicillin and amoxicillin+clavulanic acid and phenotypic confirmatory test. All the clinical isolates resistant to imipenem [IMP] were screened for the production of MBL by E-test with IMP/IMP+EDTA strips. PCR and multiplex-PCR performed for the detection of different types of ESBL producing genes in ESBL positive isolates. Of 120 the isolates, 3-5% showed MIC greater than 16 mg/ml to IMP and meropenem, 66% showed MIC greater than 32 mg/ml to ceftazidime, 42% to azteronam and 60% of the isolates showed MIC greater than 64 mg/ml to cefotaxime, 41 [34%] contlnned as ESBL producers. Not any isolate could produce MBL [p0.05]. The PCR assay of all ESBL producing isolates revealed that 6.6%, 4.1% and 2.5% of them were positive for SHY, PER and TEM genes, respectively. Many ESBL producing strains of P. aeruginosa isolated from patients in burn unit of Shafa-hospital. However, none could produce MBL enzyme. The genes among ESBL producing strains were SHY, PER as well as TEM type of b-lacatamases