Molecular characteristics and antibiotic resistance of Acinetobacter baumannii beta-lactamase-producing isolates, a predominance of intrinsic bla_OXA-51, and detection of TEM and CTX-M genes

Authors: AMIR IBRAHIMAGIC, FARAH KAMBEROVIC, SELMA UZUNOVIC, BRANKA BEDENIC, EMINA IDRIZOVIC

Abstract: Background/aim: The aim of this study was to determine the molecular characteristics and antibiotic resistance of 13 (10 inpatient and three outpatient) Acinetobacter baumannii beta-lactamase-producing isolates collected in Bosnia and Herzegovina between December 2009 and May 2010. Materials and methods: Susceptibility testing was performed by disk diffusion and broth microdilution methods. The modified Hodge and combined disk test with EDTA/phenylboronic acid was used to screen for carbapenemase production. Production of extended spectrum beta-lactamases (ESBLs) was determined by double-disk synergy test. PCR was used to detect blaESBL/blacarb genes. Results: Ten (22.2%) inpatient and three (13.6%) outpatient isolates produced beta-lactamases, ESBLs, or oxacillinases. More than 50% of the isolates showed multidrug resistance. Resistance rates to gentamicin and ciprofloxacin of the inpatients and outpatients were 80.0%, 60.0%, 75.0%, and 25.0%, respectively. MICs of carbapenems for resistant isolates ranged from 32 to >256 μg/mL. All imipenemresistant Acinetobacter baumannii strains contained bla_OXA-51. Three of the 10 inpatient isolates and one outpatient isolate containing bla_OXA-51 additionally produced other beta-lactamases (TEM/CTX-M/OXA-1). None of the inpatient or outpatient isolates were positive for other carbapenemases, especially acquired oxacillinases (bla_OXA-23/bla_OXA-24/bla_OXA-58/bla_OXA-143). Conclusion: Production of bla_OXA-51 presents an emerging threat in imipenem-resistant Acinetobacter spp. from Bosnia and Herzegovina.

Keywords: Narrow-spectrum beta-lactamases, extended-spectrum beta-lactamases, oxacillinases, antibiotic resistance

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