The mosaic architecture ofAeromonas salmonicidasubsp.salmonicidapAsa4 plasmid and its consequences on antibiotic resistance.
Aeromonas salmonicidasubsp.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 inA. salmonicidasubsp.salmonicidaand 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 inEscherichia 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-resistantA. salmonicidasubsp.salmonicidabacteria.
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.
Katherine H
KH
Tanaka
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.
Antony T
AT
Vincent
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.
Mélanie V
MV
Trudel
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.
Valérie E
VE
Paquet
Département de biochimie, de microbiologie et de bio-informatique, Université Laval, Québec, Canada; Groupe de recherche en écologie buccale (GREB), Université Laval, Québec, Canada.
Michel
M
Frenette
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.
Steve J
SJ
Charette
Aeromonas salmonicida subsp. salmonicida; Antibiotic resistance; Chloramphenicol; Comparative genomics; Insertion sequence; Integron; Plasmid; Sulfonamide; Tetracycline; pAsa4