Characterization of phenotypic and genotypic traits of carbapenem-resistant Acinetobacter baumannii clinical isolates recovered from a tertiary care hospital in Taif, Saudi Arabia

Background and objective: Acinetobacter baumannii (A. baumannii) is a common nosocomial pathogen, which developed multi-drug-resistance to different classes of antibiotics including carbapenems. This study examined ten common carbapenemase genes among 32 carbapenem-resistant A. baumannii clinical isolates recovered from Taif, Saudi Arabia. Methods: Isolates were phenotypically identified to the genus level by Vitek (R) 2 and API 20NE (R). The species level was confirmed by the amplification of bla(OXA-51). The susceptibility for 21 different antibiotics was performed by Vitek 2 and modified Kirby-Bauer method. Isolates were genetically screened for 10 carbapenemases. Phylogenetic relatedness between isolates was determined by ERIC-PCR. Results: Genotypically identified A. baumannii represented 100% of the total phenotypically identified Acinetobacter spp. All the carbapenem-resistant isolates were sensitive to polymyxin B and colistin. Among the other antibiotics, ampicillin/sulbactam and tigecycline were the most effective agents. 90.8% of the isolates were resistant to all ten investigated beta-lactams. bla(OXA-51), bla(IPM) , bla(NDM) and bla(OXA-)(23) were detected in 100%, 87.5%, 62.5% and 59.4% of isolates, respectively. Also, bla(VIM) and blaOXA-40 were less prevalent and were detected in 9.3% and 3.1% of the isolates, respectively. In addition, bla(KPC), bla(OXA-)(48) , bla(OXA-58), bla(OXA-1)(81) were not detected in any isolate. The A. baumannii isolates were categorised into ten genotypes on the basis of the detected carbapenemase genes and ERIC-PCR revealed a remarkable clonal diversity among these isolates. Conclusion: Class A and class D carbapenemase genes were the most commonly detected among carbapenem resistant A. baumannii (CRAB) clinical isolates.