Characterization of carbapenem resistant Acinetobacter baumannii isolated from intensive care units in two teaching hospitals from Algeria and Tunisia

Abstract

Introduction: This study was conducted to identify the enzymatic mechanism of carbapenem resistance in A. baumannii isolated from intensive care units of 2 teaching hospitals (Charles Nicolle hospital of Tunis and University hospital of Annaba).

Methods: Twenty seven non repetitive carbapenem-resistant A. baumannii were collected (7 strains in Algeria and 20 in Tunisia). Antibiotic susceptibility was performed by disk diffusion method. MICs were determined by agar dilution method. EDTA-disk synergy test was performed for metallo-β-lactamases (MBL) phenotypic
detection. Detection of blaOXA-23-like, blaOXA-24-like, blaOXA-51-like and blaOXA-58-like families was performed by PCR followed by sequencing. Genetic
relatedness between strains was investigated by pulsed-field gel electrophoresis (PFGE).

Results: Strains were recovered especially from respiratory tract specimens (n=12) and blood (n=11). All strains were co-resistant to all β-lactams, gentamicin, amikacin and ciprofloxacin, but remainded susceptible to colistin. MBL production was negative for all isolates. blaOXA-51-like was detected in all strains and blaOXA-23-like in 23 strains. However, blaOXA-58-like and blaOXA-24-like were not found in any isolate. Six major PFGE patterns were found in the Tunisian isolates. However, the Algerian strains were clustered in one clone.

Conclusion: This study shows a high distribution of blaOXA-23 in imipenem-resistant A. baumannii isolated in Tunisia and Algeria. It demonstrated the epidemic diffusion of this multidrug resistant pathogen. Thus, strengthening of prevention measures are required to control further spread of carbapenemases in the two countries.

Key words: A. baumannii, Carbapenem resistance, OXA-23-like, Pulsed-field gel electrophoresis