Clinical Microbiology and Antimicrobial Chemotherapy. 2019; 21(2):171-180
Objectives. To assess the rates of antibiotic resistance and production of acquired carbapenemases in nosocomial strains of Acinetobacter spp., and to determine the genotypes and prevalence of “international high-risk clones” among nosocomial strains of Acinetobacter baumannii isolated in various regions of Russia within the “MARATHON 2015–2016” study.
A total of 1005 non-duplicate nosocomial isolates of Acinetobacter spp., including 975 isolates of A. baumannii, collected in 44 hospitals from 25 cities in Russia in 2015– 2016 were studied. Species identification of isolates was performed by means of MALDI-TOF massspectrometry. Antimicrobial susceptibility was determined using broth microdilution method according to ISO 20776-1:2006 and interpreted using EUCAST MIC clinical breakpoints v.9.0. The presence of acquired carbapenemase genes of OXA-23, OXA-24⁄40, OXA-58, VIM, IMP, NDM, GES-2 and GES-5 groups was determined using real-time PCR. Genotyping of A. baumannii isolates was performed by analysis of selected single nucleotide polymorphisms in 10 chromosomal loci used for multi-locus sequence tying (MLST) of this species.
Acinetobacter spp. and A. baumannii comprised of 17.4% and 16.8% of all bacterial pathogens isolated within the “MARATHON 2015–2016” study. Resistance rates to carbapenems (imipenem and meropenem) were 77.4% and 77.1% of A. baumannii isolates, respectively. In 76.2% of A. baumannii isolates, the genes of acquired carbapenemases of molecular class D were detected, which belonged to the following groups: OXA-24⁄40 (57.5%), OXA-23 (18.4%) and OXA-58 (0.1%). Two isolates (0.2%) carried the genes of OXA-24⁄40- and OXA-23-like carbapenemases simultaneously. Most carbapenemaseproducing isolates belonged to the «international high-risk clones»: CC92/208OXF/CC2PAS (60.3%), CC944OXF/CC78PAS (25.4%) and CC109/231OXF/CC1PAS (11.6%). The vast majority of A. baumannii isolates exhibited resistance to ciprofloxacin (99.0%), amikacin (89.2%) and gentamicin (77.4%). The prevalence of resistance to tobramycin and trimethoprim/sulfamethoxazole was variable among strains of different genotypes. Colistin was the most active agent in vitro (0.9% of resistant isolates). Isolates of other Acinetobacter species were more susceptible to most antibiotics. However, two isolates of Acinetobacter ursingii and Acinetobacter baylyi carried the genes of NDM metallo-beta-lactamases.
The results of this study indicate a very high prevalence of resistance to most antibiotics, including carbapenems, in nosocomial strains of Acinetobacter spp. This makes the selection of empiric antibiotic treatment extremely difficult and urges the need for regular local surveillance of resistance in every hospital.