Spread of carbapenem-resistant Acinetobacter baumannii carrying a plasmid with two genes encoding OXA-72 carbapenemase in Lithuanian hospitals

To study the molecular epidemiology of Acinetobacter baumannii isolates from Lithuanian hospitals with an emphasis on the characterization of plasmids and antibiotic-resistance genes and their relationship with European clones (ECs) I and II. PFGE, PCR analysis of ECs and resistance genes, plasmid replicon typing, DNA transformation and sequencing were employed to characterize A. baumannii. Of the 444 isolates studied, 230 (52) and 202 (45) belonged to ECI and ECII clones, respectively, and showed clone-specific resistance gene profiles. Five plasmids from 6 to 100 kb in size in different combinations (one to four plasmids) were found in A. baumannii isolates, the combination of 9 70 kb plasmids in ECI isolates (60, 137/230) and an 11 kb plasmid in ECII isolates (52, 106/202) being the most frequent. GR2 and GR6 replicon groups, alone or in combination, were found, with a prevalence of GR2 GR6 in ECI isolates of 90 (206/230) and a prevalence of GR2 in ECII isolates of 56 (113/202). The vast majority (95, 165/174) of carbapenem-resistant A. baumannii ECII isolates carried a novel GR2-type plasmid of 11 kb, designated pAB120, which had two copies of a bla(OXA-72) gene, flanked by XerC/XerD-like sites and conferred resistance to carbapenems when introduced into a carbapenem-susceptible A. baumannii strain. The spread of carbapenem-resistant A. baumannii in Lithuanian hospitals is strongly associated with strains belonging to ECII and carrying a GR2 plasmid encoding two bla(OXA-72) genes. The genetic environment of pAB120 supports the role of site-specific recombination associated with the acquisition of carbapenem-hydrolysing class D -lactamases.