Molecular characteristics and antibiotic resistance of Acinetobacter baumanniibeta-lactamase-producing isolates, a predominance of intrinsic blaOXA-51, and detection of TEM and CTX-M genes.

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 imipenem-resistant Acinetobacter baumannii strains contained blaOXA-51. Three of the 10 inpatient isolates and one outpatient isolate containing blaOXA-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 (blaOXA-23/blaOXA-24/blaOXA-58/blaOXA-143). CONCLUSION Production of blaOXA-51 presents an emerging threat in imipenem-resistant Acinetobacter spp. from Bosnia and Herzegovina.