Variants and recombinogenic properties of attCs associated to the aacA antimicrobial resistance gene cassettes in Pseudomonas spp.

GAMBINO AS; ALONSO FM; ALVAREZ, VA; QUIROGA MP; CENTRÓN D.

Ciudad Autónoma de Buenos Aires

Congreso; Segunda Reunión Conjunta de Sociedades de Biociencias; 2017

SAIC-SAIB-SAI-SAA-SAB-SAB-SAFE-SAFIS-SAH-SAP

Pseudomonas aeruginosa is naturally sensitive to aminoglycosides.In the nosocomial niche, this species rapidly evolves to a resistant phenotypeby acquisition of antimicrobial resistance gene cassettes (ARGCs) in class 1integrons (C1I). The attC site is recognizedby the integron integrase IntI1, which allows accumulation of ARGCs in integrons. The aim of this workwas to analyze the role of the attC variantsassociated to aacA ARGCs, in thedissemination of aminoglycoside resistance within Pseudomonas and its relation with other attCs associated to other families of antibiotics.The alleles of the aacA ARGCs in the Pseudomonasand other ARGCs reference sequences were extracted from the INTEGRALL database.The attC sequences were studiedthrough ClustalW and phylogenetic trees with MEGA 6.A total of 129 C1I  belonging to P. aeruginosa (118), P. putida (9), P. mendocina (1) and P. fluorescens(1) were downloaded.  We identified 158 aacA ARGCs, with 91 attCaacA variants. The length of attCaac(6´) was 43-114nt, and attCaacA7 72-113nt. The most abundant ARGC in Pseudomonas was aac(6?)-Ib (99). A variant of attCaac(6?)-Ibwas found in 13 strains, one of them in a fused aacC1/aac(6?)-Ib ARGC. Weidentified that the aacA8 gene was onlyfound in Pseudomonas.The attCaac(6´)swere the most diverse attC sites.Variants of attCaac(6´) andattCaacA7 were scatteredin several clusters. Most of the attCsrelated to other families of antibiotics grouped separated from the other aacA clusters. Recombination assays mediated by IntI1 evidencedthat attCaac(6´)-Ibpossessed both low insertion and excision frequencies which is in concordancewith a high rate of this ARGC in clinical samples. Once inserted in the variableregion they are poorly lost. In contrast, attCsites from other ARGCs evidenced high rate of excision with a low rate ofdissemination. Together with the antibiotic pressure, the properties of attC variants could be related toepidemiological dissemination of ARGCs.