engleski

Clonal spread of carbapenem-resistant OXA-40 positive Acinetobacter baumannii in a Croatian university hospital

Abstract Objectives: Carbapenems have a potent activity against and are often used as last resort for the treatment of infections due to multiresistant Acinetobacter baumannii isolates. Recently an increase in the prevalence of carbapenem resistant A. baumannii isolates has been observed at the Clinical Hospital Center Zagreb. The aim of the study was to characterize the mechanisms of carbapenem resistance in our A. baumannii isolates. Methods:Antibiotic susceptibilities were determined by broth microdilution. Oxacillinase genes were detected by multiplex PCR. Metallo β-lactamases were detected by E-test and PCR with primers specific for VIM, IMP and SIM β-lactamases. Genotyping of the strains was performed by pulsed-field gel electrophoresis (PFGE), rep-PCR, random amplification of polymorphic DNA (RAPD), and determination of sequence groups according by multiplex PCR. Results:Thirty three clonally related strains were were positive for blaOXA-40. One unrelated isolate was positive for blaOXA-58. The nine remaining isolates possessed only the naturally ocurring OXA-51 β-lactamase which was associated with ISABaI insertion sequence in five strains. No metallo β-lactamase genes were found. The blaOXA-40 positive isolates were shown to be clonally related by RAPD rep-PCR and PFGE. Other isolates showed distinct PFGE and RAPD patterns. The isolates producing only OXA-51 β-lactamase were found to belong to EU clone 1 (sequence group II) whereas the OXA-40 and OXA-58 producers belonged to EU clone 2 (sequence group I). Conclusions: On the basis of susceptibility testing, β-lactamase characterization and genotyping of the strains we can conclude that spread of endemic isolates was responsible for high frequency of detection of OXA-40- like positive multidrug-resistant A. baumannii in this setting. Most of the strains originated from the ICU indicating local dissemination within the hospital and pointing to the potential source of isolates. Colistin is the only therapeutic option in most cases. High rate of resistance to ampicillin/sulbactam is worrying and is probably due to the production of TEM-1 β-lactamase.

Acinetobacter baumannii ; OXA-40 ; OXA-58 ; meropenem ; imipenem

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