Detection of TEM, SHV and PER Type Extended-Spectrum ß-Lactamase Genes among Clinical Strains of Pseudomonas aeruginosa Isolated from Burnt Patients at Shafa-Hospital, Kerman, Iran

Objective(s) This study was carried out to evaluate the existence of the TEM, SHV and PER ESBL genes in ESBL producing strains of Pseudomonas aeruginosa isolated from burnt patients at Shafa-hospital, Kerman, Iran. Materials and Methods 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. Results Of 120 the isolates, 3-5% showed MIC greater than 16 µg/ml to IMP and meropenem, 66% showed MIC greater than 32 µg/ml to ceftazidime, 42% to azteronam and 60% of the isolates showed MIC greater than  64 µg/ml to cefotaxime, 41 (34%) confirmed as ESBL producers. Not any isolate could produce MBL (P≤0.05). The PCR assay of all ESBL producing isolates revealed that 6.6%, 4.1% and 2.5% of them were positive for SHV, PER and TEM genes, respectively. Conclusion 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 SHV, PER as well as TEM type of β-lacatamases.