Antimicrobial resistance of nosocomial Acinetobacter spp. isolates in Russia: results of multicenter epidemiological study «MARATHON» 2013-2014

Abstract

Acinetobacter baumannii and related species of the A. baumannii complex are the common and one of the most difficult-to-treat nosocomial pathogens. In this paper, we report the data on antimicrobial susceptibility of 568 isolates of Acinetobacter spp., including 542 A. baumannii, collected in 31 hospitals of 21 cities of Russia in 2013-2014 as part of the national multicenter surveillance study on antimicrobial resistance of nosocomial pathogens, «MARATHON». Acinetobacter spp. and, specifically, A. baumannii isolates comprised, respectively, 14.4% and 13.7% of all bacterial nosocomial isolates. In A. baumannii, the non-susceptibility rates to carbapenems were: 74.7% to meropenem, 79.9% to doripenem, and 70.9% to imipenem; the genes for acquired molecular class D carbapenemases were detected in 63.5% of isolates. Those included the genes for OXA-²⁴⁄₄₀-like (39.7%), OXA-23-like (23.8%) и OXA-58-like (0.6%) enzymes (three isolates carried simultaneously the genes for OXA-23- and OXA-²⁴⁄₄₀-like β-lactamases). Most of the isolates were insusceptible to ciprofloxacin (98.0%), to aminoglycosides: gentamicin (71.2%), amikacin (88.0%) and netilmicin (61.0%), and to trimethoprim/sulfamethoxazole (68.5%). Colistin had the highest in vitro activity with resistance rate being as low as 1.9%. A total of 47.1% and 82.1% isolates had the MICs of tigecycline and sulbactam exceeding the epidemiological cut-off values of 1 mg/l and 4 mg/l, respectively. Notably, 98.0% of the A. baumannii isolates were categorised as multidrug resistant (MDR) and 64.4% - as extensively drug-resistant (XDR).