Evaluation of metallo-betalactamase and carbapenemase activity in Pseudomonas aeruginosa strain isolated from clinical samples in Tehran

Pseudomonas aeruginosa is an opportunistic pathogen and a major cause of nosocomial infections. Metallobetalactamases and carbapenemases are the most important factors in resistance to carbapenem drugs in Pseudomonas aeruginosa strains. The aim of this study was to evaluate the activity of metallobetalactamase and carbapenemase in Pseudomonas aeruginosa isolated from clinical specimens. 49 strains of Pseudomonas aeruginosa isolated from patients admitted to the intensive care unit were identified by biochemical methods, then their antibiotic susceptibility was determined by Kirby- Bauer method. MBL producing strains were identified by phenotypic method combined disk test and KPC- producing strains were evaluated by MHT method. PCR method was also used to identify strains carrying VIM, SIM, GIM, SPM and IMP genes. Antibiotic resistance to ticarcillin, meropenem, gentamicin, ciprofloxacin, cefpime and ceftazidime were 89.8%, 51%, 44.9%, 67.4%, 93.9%, 95.9%, respectively. By phenotypic analysis combined disk test, 55.1% of the strains were identified as metallo-betalactamase producing strains. Also, 38.8% of carbapenemase producing strains were observed by MHT method. The frequencies of each of these gene’s VIM, SIM and GIM were 63.3%, 38.8%, 34.7%, respectively, and SPM and IMP genes were not observed in any of the strains in this study.