A NOVEL GENETIC PLATFORM INVOLVED IN BLAOXA-58 DISSEMINATION AMONG Acinetobacter baumannii STRAINS

CAMERANESI MARÍA M.; MORAN BARRIO, J.; BRAMBILLA, L.; LIMANSKY, A.; VIALE A.M.

Mar del Plata

Congreso; Reunion SAIB; 2014

SAIB

The emergency of carbapenem resistance in Acinetobacter baumannii is most frequently the result of the over-production of carbapenem hydrolyzing OXA-type β-lactamases (CHβL), a process generally mediated by the insertion of different insertion sequences (IS) upstream of blaOXA-58 genes thus generating stronger promoters. We report the genetic surroundings of blaOXA-58 in plasmid pAb242 extracted from a local carbapenem resistant clinical A. baumannii strain. blaOXA-58 is embedded in an imperfect composite Tn3-like transposon, in which the upstream ISAba3 was targeted by an ISAba825. The ISAba825 insertion site differs from other target sites present in similar arrangements in other A. baumannii strains, indicating a different evolutionary origin of this particular arrangement. Analysis of the downstream region of the 3´-located ISAba3 identified araC1 and lysE regulatory genes, the latter disrupted by a novel insertion of a composite Tn125 transposon bearing an active aphA6 gene conferring aminoglycoside resistance. The whole arrangement described above was also bracketed by Re27-like short sequences, thus providing potential recombination sites for the mobilization intra- and inter-genomes of this platform. Evolution of these flexible genetic structures bearing blaOXA-58 may likely contribute to the rapid worldwide spread of CHβL genes among the global A. baumannii population.