Background & Objectives : Acinetobacter baumannii is an opportunistic Gram-negative pathogen with increasing relevance in a variety of hospital-acquired infections especially among intensive care unit patients. A. baumannii is mostly a cause of septicemia, pneumonia and urinary tract infection following hospitalization of patients. In this study antibiotic susceptibility pattern of A.baumannii isolates and molecular typing among isolates resistant by REP-PCR were determined.

  Methods : During study, the A. baumannii, were isolated from hospitals in Tehran. The isolates were identified using standard biochemical tests and antibiotic susceptibility was determined by the disk diffusion method. Extraction of DNA and molecular typing of isolates performed using CTAB method and REP-PCR, respectively.

  Results : In this study 75 A. baumannii isolates separated from patients with an average age of 51 ± 18.45 years . The highest resistance rate was against azteronam (97%), ceftazidim (93%), cefepime (93%), piperacillin-tazobactam (93%), ciprofloxacin (93%) and ticarcillin (93%) while the lowest resistance rate was against tigecycline (n= 51, 68%), followed by tobramycin (n=24, 32%), ampicillin-sulbactam (n=21, 28%), amikacin (n=16, 21%), and carbapenems (n=11, 15%). The REP-PCR in resistant of A. baumannii isolates showed that the genotypes of A, B and C are the predominant genotypes in the resistant antibiotics.

  Conclusion: This study showed a high percentage of resistance to antimicrobial agents among genotypes A, B, and C of the A. baumannii isolates therefore strategies to control the spread of A. baumannii isolates must be designed and evaluated.