Antimicrobial Susceptibility Pattern and Prevalence of Extended-Spectrum β-Lactamase Genotypes among Clinical Isolates of Acinetobacter baumanii in Tabriz, North-West of Iran

Multidrug resistant (MDR) Acinetobacter baumanii strains have emerged as novel nosocomial pathogens threatening patients’ lives, especially in intensive-care units (ICU). Various types of extended-spectrum β-lactamases (ESBLs) are involved in conferring resistance to β-lactam antibiotics, making their genotypic characterization an essential prerequisite to take proper preventative measures.
The aim of this study was to determine the antimicrobial susceptibility and prevalence of blaTEM, blaSHV, blaCTX-M, blaOXA-2, and blaOXA-10 genes among A. baumanii isolates obtained from patients in Tabriz city, North-west Iran.
The clinical isolates of A. baumanii were collected from patients hospitalized in the Imam Reza hospital of Tabriz. Antimicrobial susceptibility patterns were determined by the disk diffusion method. The frequency of different ESBLS resistance genes were determined by PCR.
Antimicrobial susceptibility testing through the disk diffusion method revealed that the lowest resistance rates were against polymyxin B (16%), colistin (23%), and rifampin (27%); whereas the highest resistance rate was observed against ticarcillin (100%), cefixime (100%), and ceftizoxim (100%). Screening by double disk synergy test showed that 60% of the isolates were ESBL producers. PCR technique on ESBL-positive isolates determined blaSHV gene as the most prevalent (31.6%) and blaOXA-10 as the least prevalent (8.3%) among the studied resistance genes.
The high prevalence of resistance genes supported the essential role of ESBLs in antibiotic resistance of A. baumanii.