Clinical Isolates of Acinetobacter baumannii From Tehran Hospitals: Pulsed-field Gel Electrophoresis Characterization, Clonal Lineages, Antibiotic Susceptibility, and Biofilm-forming Ability

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.
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.
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.
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.
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.