Survey of Antibiotic Resistance and Frequency of blaOXA-23 and blaOXA-24 Oxacillinase in Acinetobacter baumannii Isolated from Tracheal Tube Specimens of Patients Hospitalized in Intensive Care Units in Isfahan city

Acinetobacter baumannii is a non-fermentative gram-negative coccobacill that is prevalent in intensive care units. Carbapenem resistant A.baumannii isolates have been reported worldwide. Oxasillinase beta-lactamase enzymes are involved in bacterial resistance to carbapenem. This study aimed to determine the prevalence of blaOXA-23 and blaOXA-24 genes in A. baumannii isolated from tube discharge specimens of hospitalized patients in the intensive care units of the hospitals in Isfahan, Iran, in 2015.
A total of 40 isolates of A. baumannii were collected from the patients admitted to the intensive care units of the hospitals in Isfahan in 2015, they were identified by biochemical methods and detection of blaOXA-51 like gene. Antibiotic resistance pattern and minimum inhibitory concentration of imipenem were determined using disk diffusion and E-test methods respectively according to CLSI2015 protocol. blaOXA-23 and blaOXA-24 genes were detected by PCR method. Data were analyzed by SPSS (v.16) software and chi-square tests.
All isolates were found resistant to ceftazidime, ceftriaxone, meropenem and imipenem and the lowest resistance were seen against colistin (0%) and tigecycline (10%), respectively. All isolates were resistant to imipenem using Etest method with MIC ≥ 32 μg / ml. blaOXA-23 and blaOXA-24 genes were detected in 87.5% and 25% of isolates, respectively.
Due to the results, treatment of A. baumannii isolates by carbapenems is ineffective and tigecycline or colistin could be used for treatment. Other studies for detection of other mechanisms for carbapenem resistance are recommended.