Background: Acinetobacter baumannii is known as a potential pathogen in hospitals and is responsible for the dramatic increase in carbapenem resistance in Iran in the recent years. Objectives: The current study aimed at determining the genetic association of the isolates by the pulsed-field gel electrophoresis (PFGE) technique, identify international clones, evaluate biofilm formation ability and its relationship with antibiotic resistance. Methods: In the current study, a total of 48 A. baumannii isolates were collected from 2 hospitals in Tehran, Iran, from 2010 to 2012. Isolates were subjected to antimicrobial susceptibility testing, determination of carbapenemase encoding genes, biofilm formation, and genetic relationships analysis. Results:The obtained results demonstrated that the rate of resistance to carbapenem, meropenem, imipenem, and doripenem was 76%. The carbapenemase-encoding gene blaOXA-23-like was found in 32 isolates, while blaOXA-40-like (blaOXA-24-like), blaOXA-58-like, blaVIM-type and blaIMP-type were found in 11, 1, 19. and 5 isolates, respectively. When the lineage of the isolates was evaluated by the multiplex polymerase chain reaction (PCR), it was found that 28 isolates belonged to group 1 and 8 isolates to group 2. None of the isolates belonged to group 3. Twelve isolates could not be typed by this method. The study findings interestingly demonstrated that 13 isolates showed no biofilm formation. Data of biofilm formation also demonstrated that 28, 4, and 3 remaining isolates had weak, moderate, and strong biofilm formation, respectively. The pulsed field gel electrophoresis result revealed 11 unique clones. Conclusions: International clone 1 was the most commonly identified clone in the current study. This clone was mostly associated with blaOXA-23-like gene; therefore, 64% of the isolates in this clone possessed blaOXA-23-like gene.

Background: Despite a relatively low virulence of Acinetobacter baumannii isolates, emerging multidrug-resistant (MDR) strains to pose a formidable threat to patients, particularly in ill patients in intensive care unit (ICU). Objectives: The aim of the present study was to determine the genetic relatedness and antimicrobial susceptibility patterns in the endemic clones of A. baumannii isolated from patients in the ICU. Methods: Fifty-five non-repetitive A. baumannii isolates were examined for antimicrobial susceptibility, oxacillinase genes, class 1 integrons and genetic relationships by PFGE. Results: Antibiotic susceptibility testing showed that 21.8%) 12 isolates) were resistant to all tested antibiotics. Resistant to carbapenems were up to 85%. OXA-23, OXA-24 and OXA-58 genes were detected in 81.81%, 16.36% and 1.81% isolates respectively. The ISAba1 element upstream of blaOXA-51 was detected in 18 (32%) isolates, and 22 (40%) isolates had an ISAba1 insertion sequence upstream of the blaOXA-23. Integron class 1 was detected in 25 (55.5%) OXA-23 carrying isolates, 2 (22.2%) in OXA-24 positive isolates and in one OXA-58 carrying isolate. PFGE analysis resolved 50 distinct pulsotypes, Most of the isolates were scattered throughout across the dendrogram and a few grouped as clusters. Conclusions: No significant association has been found between the pulsotype of each isolate and MDR patterns and the presence of carbapenemase genes, however, highly resistant blaOXA-23 gene carrying endemic clones of A. baumannii disseminated in the ICU of two hospitals. Therefore, active surveillance and health policies are urgently needed for the detection and control the dissemination of such organisms.