The mosaic architecture of Aeromonas salmonicida subsp. salmonicida pAsa4 plasmid and its consequences on antibiotic resistance

Katherine H Tanaka; Antony T Vincent; Mélanie V Trudel; Valérie E Paquet; Michel Frenette; Steve J Charette

doi:10.7717/peerj.2595

The mosaic architecture of Aeromonas salmonicida subsp. salmonicida pAsa4 plasmid and its consequences on antibiotic resistance

PeerJ. 2016 Oct 27:4:e2595. doi: 10.7717/peerj.2595. eCollection 2016.

Authors

Katherine H Tanaka¹, Antony T Vincent¹, Mélanie V Trudel¹, Valérie E Paquet¹, Michel Frenette², Steve J Charette¹

Affiliations

¹ Institut de biologie intégrative et des systèmes, Québec, Canada; Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada; Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Québec, Canada.
² Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Québec, Canada; Groupe de recherche en écologie buccale (GREB), Université Laval, Québec, Canada.

Abstract

Aeromonas salmonicida subsp. salmonicida, the causative agent of furunculosis in salmonids, is an issue especially because many isolates of this bacterium display antibiotic resistances, which limit treatments against the disease. Recent results suggested the possible existence of alternative forms of pAsa4, a large plasmid found in A. salmonicida subsp. salmonicida and bearing multiple antibiotic resistance genes. The present study reveals the existence of two newly detected pAsa4 variants, pAsa4b and pAsa4c. We present the extensive characterization of the genomic architecture, the mobile genetic elements and the antimicrobial resistance genes of these plasmids in addition to the reference pAsa4 from the strain A449. The analysis showed differences between the three architectures with consequences on the content of resistance genes. The genomic plasticity of the three pAsa4 variants could be partially explained by the action of mobile genetic elements like insertion sequences. Eight additional isolates from Canada and Europe that bore similar antibiotic resistance patterns as pAsa4-bearing strains were genotyped and specific pAsa4 variants could be attributed to phenotypic profiles. pAsa4 and pAsa4c were found in Europe, while pAsa4b was found in Canada. In accordance with their content in conjugative transfer genes, only pAsa4b and pAsa4c can be transferred by conjugation in Escherichia coli. The plasticity of pAsa4 variants related to the acquisition of antibiotic resistance indicates that these plasmids may pose a threat in terms of the dissemination of antimicrobial-resistant A. salmonicida subsp. salmonicida bacteria.

Keywords: Aeromonas salmonicida subsp. salmonicida; Antibiotic resistance; Chloramphenicol; Comparative genomics; Insertion sequence; Integron; Plasmid; Sulfonamide; Tetracycline; pAsa4.

Grants and funding

This work was supported by the Fonds de la recherche québécois sur la nature et les technologies (FRQNT) (B1 scholarship to KHT and B2 scholarship to ATV), the Natural Sciences and Engineering Research Council of Canada (NSERC) (Alexander Graham Bell Canada Graduate Scholarships to KHT and ATV and Discovery grant RGPIN-2014-04595 to SJC), Ressources Aquatiques Québec (RAQ) (CREATE scholarship to MVT and a grant to MF), and the Innovamer Program of the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.