Antibiotic Resistance Profile and Distribution of Oxacillinase Genes Among Clinical Isolates of Acinetobacter baumannii in Shiraz Teaching

Background: The emergence of multidrug-resistant Acinetobacter baumannii complicates the therapy of the related infections. Hospital isolates of A. baumannii are usually multidrug-resistant. The problem is compounded by increasing resistance to broad-spectrum antibiotics including carbapenems. Objectives: The aim of this study was to determine antimicrobial susceptibility patterns and distribution of blaOXA-type carbapenemases genes among A. baumannii isolates from hospitalized patients in Shiraz, Southwest Iran. Materials and Methods: Two hundred A. baumannii isolates were recovered from different clinical specimens in four Shiraz teaching hospitals. Isolates were detected as A. baumannii by Microgen kit and PCR with specific primers of blaOXA-51-like gene. Antimicrobial susceptibility testing was determined by disk diffusion method for all the isolates. Multiplex PCR assays were performed for detection of blaOXA-23-like, blaOXA-24-like and blaOXA-58-like genes. Results: All the isolates were susceptible to colistin and polymyxin B. Moreover, all of them were resistant to piperacillin, piperacillintazobactam, ampicillin, ceftazidime, cefoxitin and aztreonam. Eighty (40%) isolates had positive results for blaOXA-23-like, 14 (7%) for blaOXA24-like and 1 (0.5%) isolate for blaOXA-58-like. The co-existence of studied genes was detected for blaOXA-23-like plus blaOXA-24-like in nine (4.5%) isolates. Conclusions: The prevalence of carbapenem resistant A. baumannii isolates in Shiraz hospitals is high. The blaOXA-23-like gene was the most frequent carbapenemase identified among resistant A. baumannii isolated in Shiraz hospitals. The increasing incidence of A. baumannii is a serious concern, therefore control of this pathogen and taking preventive measures are emphasized.