Carbapenem resistance and acquired class D beta-lactamases in Acinetobacter baumannii from Croatia 2009–2010

Abstract

The molecular epidemiology and the genetic basis of carbapenem resistance was investigated in 185 Acinetobacter baumannii isolates obtained from 13 centers of northern Croatia and Istria during 2009-2010. All isolates were multidrug-resistant, and 35 % (n = 64) were resistant to both imipenem and meropenem. ISAba1-driven overexpression of the intrinsic bla OXA-51-like gene was observed in all carbapenem resistant isolates, and 69 % of these (n = 44) also produced acquired OXA-type carbapenemases. The presence of bla OXA-58-like, bla OXA-24/40-like, and bla OXA-23-like genes was demonstrated in 33 % (n = 21), 27 % (n = 17) and 9 % (n = 6) of carbapenem-resistant isolates, respectively. None of the isolates harbored the bla IMP, bla VIM, bla SIM, bla NDM or bla PER β-lactamase genes, while bla TEM-1 was detected in five carbapenem- and ampicillin/sulbactam-resistant isolates. Sequence group determination showed a high prevalence (81 %) of isolates belonging to the International clonal lineage (ICL)-I, although the majority (80 %) of isolates carrying acquired carbapenemase genes belonged to the ICL-II. Random amplified polymorphic DNA analysis and multilocus-sequence typing of a subset of carbapenem-resistant isolates revealed a low degree of genetic variability within both ICL-I and ICL-II populations, irrespective of the genetic basis of carbapenem resistance. Overall, an increasing trend toward carbapenem resistance was observed for A. baumannii in Croatia, and the emergence of ICL-II strains producing a variety of acquired carbapenemases.