Polyclonal Distribution of blaOXA-23 Gene Among Acinetobacter baumannii Isolated from Intensive Care Unit Patients in Tehran; Pulsed-Field Gel Electrophoresis Analysis

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).
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.
Fifty-five non-repetitive A. baumannii isolates were examined for antimicrobial susceptibility, oxacillinase genes, class 1 integrons and genetic relationships by PFGE.
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.
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.