High frequency of carbapenemase in extensively drug-resistant Acinetobacter baumannii isolates in central Iran.

Objectives: We assessed the frequency of occurrence for infections caused by wild-type A. baumannii, multidrug-resistant (MDR) or XDR A. baumannii, and CRAB. We detected different antibiotic resistance genes in the genomes of infectious A. baumannii strains from central Iran.

Methods: This study investigated 546 clinical patient samples for the presence of A. baumannii by using conventional culture methods and PCR. Antibiotic resistance profiles, and the phenotypic and genotypic characteristics of various antibiotic genes were analyzed.

Results: Out of 546 samples, 87 (15.9%) A. baumannii isolates were obtained using culture and all culture positive samples were also positive by PCR. The most effective antibiotics were polymyxin B (n = 84 strains) (96.6% susceptibility), colistin (n = 81) (93.1%), and ampicillin/sulbactam (n = 18) (20.7%). All clinical A. baumannii isolates were ESBL-positive. The number of CRAB was 84 (96.5%). All CRAB isolates were both MDR and XDR. Of all CRAB isolates, 78 out of 84 (92.4%) produced metallo-β-lactamase (MBL) by phenotypic diagnosis. The most abundant genes were bla (32/87; 36.7%), bla (29/87; 33.3%), bla (26/87; 29.8%) for ESBL and Ambler class D β -lactamases included bla (69/84; 82.1%), bla (46/84; 54.7%), MBLs included bla (51/84; 60.7%), and bla (28/84; 33.3%) for carbapenemase.

Conclusion: High frequencies of XDR A. baumannii and CRAB (96.5%) were detected in central Iran. Quick and accurate diagnosis, appropriate isolation of patients colonized or infected by CRAB isolates, application of accurate and effective infection control policies and programs, and appropriate preventive measures are deemed helpful in preventing the further spread of these resistant and clinically highly relevant strains.