Carbapenem-resistant Acinetobacter baumannii: Current status of the problem in four Bulgarian university hospitals (2014-2016)

Objectives: A total of 226 carbapenem-resistant Acinetobacter baumannii (CRAB) isolates was collected during 2014-2016 from inpatients (age range 5-88 years) in four Bulgarian university hospitals (H1-H4) to assess their antimicrobial susceptibility and to explore carbapenem resistance mechanisms as well as the molecular epidemiology of the isolates. Methods: Antimicrobial susceptibility testing, multiplex PCR, DNA sequencing and electrotransformation experiments were performed. Epidemiological typing by random amplification of polymorphic DNA (RAPD)-PCR was also performed. Results: The resistance rates were as follows: imipenem, 90.7%; meropenem, 98.2%; doripenem, 100%; amikacin, 92.9%; gentamicin, 87.2%; tobramycin, 55.8%; levofloxacin, 98.2%; trimethoprim/sulfamethoxazole, 86.3%; tigecycline, 22.1%; colistin, 0%; and ampicillin/sulbactam, 41.6%. Intrinsic bla(OXA-51-like) genes were found in all of the isolates. The majority of the A. baumannii isolates harboured either bla(OXA-23-like) associated with the upstream-located ISAba1 (26.1%) or bla(OXA-40/24-like) (46.7%), 45 isolates (19.9%) harboured both genes, and 1 isolate harboured bla(OXA-58-like )surrounded by ISAba3C upstream and ISAba3 downstream. The bla(OXA-58) gene was transferable by electroporation indicating its plasmid location. Epidemiological typing revealed the dissemination of nosocomial CRAB with high clonal relatedness (70% similarity threshold) belonging to six, four, three and two clusters in H1, H2, H3, and H4 hospitals, respectively. Conclusions: The A. baumannii isolates studied were problematic nosocomial pathogens. Their multidrug resistance greatly limits therapeutic options. The persistence of endemic clones comprised of OXA carbapenemase-producing multidrug-resistant A. baumannii in the monitored hospitals over a period of ca. 3 years is of concern and requires continuous detailed investigations in the future. (C) 2018 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.