The Acinetobacter baumannii XerC/D site-specific recombination system modulates plasticity of plasmids carrying genetic elements conferring blaOXA-58-mediated carbapenem resistance

REPIZO, GUILLERMO D.; CAMERANESI, MA. MARCELA; LIMANSKY, ADRIANA S.; MORÁN-BARRIO, JORGELINA; VIALE, ALEJANDRO M.

San Miguel de Tucumán

Congreso; XII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE; 2017

Asociación Civil de Microbiología General SAMIGE

The Acinetobacter baumannii XerC/D site-specific recombination system modulates plasticity of plasmids carrying genetic elements conferring blaOXA-58-mediated carbapenem resistanceEl sistema de recombinación sitio-específico XerC/D de Acinetobacter baumannii modula la plasticidad de plásmidos portadores de plataformas de resistencia a carbapenemes mediada por blaOXA-58 Cameranesi, M.M1, Morán-Barrio, J.1, Repizo, G.D1, Limansky, A.S1, Viale, A.M.11Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET), Depto. Microbiología, FCByF, UNR, Argentina. E-mail: cameranesi@ibr-conicet.gov.arPlasmids from Acinetobacter are considered to be key genetic factors in the spread of multidrug resistance (MDR). It has been reported the presence of XerC/D-like sites flanking discrete DNA modules carrying the blaOXA plasmid-borne genes, which suggests that their dissemination in the Acinetobacter is mediated by site-specific recombination. We characterized here the plasmids carried by two clonally-related MDR A. baumannii clinical strains Ab242 and Ab825 belonging to the CC104 clonal complex in order to follow the evolution of mobile elements harboring resistance genes.Sequencing of Ab242 and Ab825 plasmids was done by 454 pyrosequencing method. They were classified on the basis of A. baumannii PCR-based replicon typing method. Plasmids bearing resistance determinants isolated from these bacteria were thoroughly characterized by cloning, sequencing and database searching. Their dissemination was evaluated by their ability to confer resistance to sensitive A. baylyi strains. We detected novel plasmids in both strains by sequencing, for the case of Ab242: pAb242_9 (9 kbp), pAb242_12 (12 kbp) and pAb242_25 (25 kbp); and for Ab825: pAb825_12 (12 kbp) and pAb825_34 (34 kbp). pAb242_9 contains a replicase (Rep) belonging to GR4 group; the pAb242_12 Rep shares 50% of identity with GR12 Rep; and pAb242_25 is a multi-replicon which harbors a RepB corresponding to GR10, and its additional Rep shows 100% of amino acidic identity with Rep of A. baumannii p11921. The pAb825_12 is identical to that described for Ab242, and pAb825_34 is a multimer formed by the junction of pAb242_25 and pAb242_12. The pAb242_25 carries a genetic element (9.6 Kbp) including ISAba825-blaOXA-58 and aphA6 flanked by XerC/D-like sites. This whole structure was found in opposite orientations within both pAb242_25 and pAb825_34 plasmids revealing thus its inversion mediated by XerC/D-sites. Deeper analyses uncovered the presence of XerC/D-like sites distributed around all mentioned plasmids. Seventeen different XerC/D-like sites were found and a consensus site was obtained. In addition, a concatemer formation between pAb242_25 and pAb242_12 through XerC/D-like sites was observed upon A. baylyi bacterial transformation employing Ab242 plasmid content. Thus, the pAb242_37 cointegrate uncovers that these sites are involved in recombination events. Further analysis of Ab242 plasmidic regions delimited by XerC/D-like sites exposed a high degree of identity with others from Acinetobacter plasmidome, suggesting that these structures could be mobilized by recombination processes.Overall evidences suggest that these sites are involved in recombination events (platforms inversion and cointegrates formation) leading to the mobilization of the resistance genes. These observations add up to the diversity of genetic plasticity mechanisms that modulate plasmid evolution and shed light on the mechanisms involved in the antimicrobial resistance dissemination.