Beta-lactamases producing acinetobacter baumannii effect on the development of cross-resistance to aminoglycosides

Abstract

Introduction. Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen that possesses not only intrinsic resistance to many classes of antibiotics, but also has a propensity for rapid development of antimicrobial resistance during treatment. Aim. The aim of our study was to investigate the effect of cross-re istance to aminoglycosides in A. baumannii strains producing β-lactamases. Materials and methods. All clinical cultures positive for A. baumannii were analyzed. A 4-disc detection kit (Abtek Biologicals, UK) was used to determine the production of the extended spectrum β-lactamase (ESBL) and AMPC β-lactamase: cefotaxime 30 μg (CTX 30), cefotaxime 30 μg plus clavulanate 10 μg CXV 40), cefotaxime 30 μg plus cloxacillin 200 μg (CTC 230), cefotaxime 30 μg plus cloxacillin 200 μg plus clavulanate 10 μg (CCC 240). If the zone of inhibition around CXV 40 disc was mea sured ≥5 mm larger than around CXT 30 disc, strain was determined to be an ESBL producer strain. If the zone of inhibition around CTC 230 disc was mea sured ≥5 mm larger than around CXT 30 disc, or around CCC 240 disc was measured ≥5 mm larger than around CXV 40 disc, or around CCC 240 disc was measured <5 mm larger than around CTC 230 disc, strain was determined to be an AMP-C producer strain. The study data were analyzed by the Statistical Package for Social Sites, version 20. Combination of meropenem disc, EDTA and boronic acid test was used to determine the production of the KPC carbapenemases. The interpretation of test results was based on the comparison between the inhibition zones of the four meropenem discs. In case of KPC production, an in crease of ≥5 mm of inhibition zone around the discs with boronic acid was observed. The Chi-square ( ᵪ²) criterion was used to evaluate qualitative data. The results were considered statistically significant at p<0.05. [...].