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 ۱۲۰ strains of P. aeruginosa were isolated from ۲۴۵ patients in burn unit of Shafa-hospital during January ۲۰۰۶ to December ۲۰۰۷. 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 ۱۲۰ the isolates, ۳-۵% showed MIC greater than ۱۶ µg/ml to IMP and meropenem, ۶۶% showed MIC greater than ۳۲ µg/ml to ceftazidime, ۴۲% to azteronam and ۶۰% of the isolates showed MIC greater than  ۶۴ µg/ml to cefotaxime, ۴۱ (۳۴%) confirmed as ESBL producers. Not any isolate could produce MBL (P≤۰.۰۵). The PCR assay of all ESBL producing isolates revealed that ۶.۶%, ۴.۱% and ۲.۵% 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.