XerC/D site-specific recombination mediates plasmid plasticity and dissemination of blaOXA-58 containing structures in Acinetobacter baumannii strains isolated in Argentina

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

Sevilla

Simposio; 11th International Symposium on the biology of Acinetobacter; 2017

XerC/D site-specific recombination mediates plasmid plasticity and dissemination of blaOXA-58 containing structures in Acinetobacter baumannii strains isolated in ArgentinaXerC/D site-specific recombination in A. baumannii resistance plasmidsCameranesi MM, Morán-Barrio J, Repizo GD, Limansky AS, Viale AM. Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET), Dept. Microbiología, FCByF, Universidad Nacional de Rosario, Rosario, Argentina. E-mail: viale@ibr-conicet.gov.arObjectives. Plasmids are considered key factors in the dissemination of multi-drug resistance determinants (MDR) among resident pathogens in the clinical setting. The presence of XerC/D-like sites flanking discrete DNA modules in plasmids carrying blaOXA genes present in clinical A. baumannii strains suggests that carbapenem resistance dissemination may be mediated by a XerC/D site-specific recombination mechanism (1,2). We studied this possibility in plasmids isolated from clonally-related MDR A. baumannii clinical strains of Argentina. Methods. The MDR carbapenem-resistant A. baumannii clinical strains Ab242 and Ab825 (assigned to CC104, Oxford nomenclature) were isolated from inpatients in a public hospital of Rosario, Argentina. Plasmid DNA from each strain was extracted and subjected to 454 pyrosequencing, and the obtained sequences were characterized by database searching (BLAST), organized, and the sequence verified by PCR with specific primers. The ability of the identified plasmids to spread antimicrobial resistance was analyzed by transformation of susceptible Acinetobacter strains followed by imipenem selection and plasmid analysis on resistant clones.Results. Sequencing analysis disclosed the presence of novel plasmids both in Ab242 (designated pAb242_25, pAb242_12, and pAb242_9) and Ab825 (designated pAb825_34 and pAb825_12). In silico analysis identified the presence of several XerC/D-like sites in these plasmids. In particular, in pAb242_25 XerC/D sites were found flanking a novel genetic structure carrying both blaOXA-58 and aphA6 resistance genes. Remarkably, this structure was found in an opposite orientation in pAb825_34, strongly suggesting an inversion process mediated by the identified XerC/D-sites. Moreover, pAb825_34 was found to represent a concatemer structure constituted by plasmids pAb242_9 and pAb242_25 generated by XerC/D site-specific recombination. Finally, transformation assays of susceptible Acinetobacter strains employing plasmid DNA from Ab242 followed by plasmid analysis of the transformants revealed a novel concatemer formed by pAb242_25 and pAb242_12, also generated by XerC/D mediated recombination. The latter result also suggested that the concatemer represented the transforming structure. Conclusions. The overall results indicate that XerC/D site-specific mediated recombination is a relevant mechanism of plasticity among A. baumannii plasmids and responsible for the mobilization of blaOXA-58 resistance structures. These results add to the plethora of dissemination mechanisms of resistance genes among MDR A. baumannii in the clinical setting.(1) Poirel and Nordmann. 2006. Antimicrob Agents Chemother 50:1442?1448.(2) Merino et al. 2010. Antimicrob Agents Chemother 54:2724?2727.