MQM1, a bacteriophage infecting strains of Aeromonas salmonicida subspecies salmonicida carrying Prophage 3

• Published in: Virus research 2023-09, Vol.334, p.199165-199165, Article 199165
• Main Authors: Hosseini, Nava, Paquet, Valérie E., Marcoux, Pierre-Étienne, Alain, Charles-Antoine, Paquet, Maude F., Moineau, Sylvain, Charette, Steve J.
• Format: Article
• Language: English
• Subjects: Aeromonas salmonicida subsp. salmonicida; furunculosis; phage cocktail; phage therapy; Prophage 3; vB_AsaP_MQM1
• ISSN: 0168-1702; 1872-7492
• DOI: 10.1016/j.virusres.2023.199165

•vB_AsaP_MQM1 (or MQM1) is a newly isolated virulent podophage.•MQM1 is highly specific to A. salmonicida subsp. salmonicida strains.•MQM1 is capable of infecting a broad range of Prophage 3-bearing strains.•MQM1 has no integrase or transposase-encoding genes.•Addition of MQM1 in a phage cocktail resolves the Prophage 3-resistance issue. Aeromonas salmonicida subsp. salmonicida is a Gam-negative bacterium responsible for furunculosis in fish. Because this aquatic bacterial pathogen has a rich reservoir of antibiotic-resistant genes, it is essential to investigate antibacterial alternatives, including the use of phages. Yet, we have previously demonstrated the inefficiency of a phage cocktail designed against A. salmonicida subsp. salmonicida strains due to a phage resistance phenotype associated to a prophage, namely Prophage 3. To bypass this resistance, one of the solutions is to isolate novel phages capable of infecting Prophage 3-bearing strains. Here we report on the isolation and characterization of the new virulent phage vB_AsaP_MQM1 (or MQM1), which is highly specific to A. salmonicida subsp. salmonicida strains. Phage MQM1 inhibited the growth of 01-B516, a strain carrying Prophage 3, including when combined to the previous phage cocktail. MQM1 infected 26 out of the 30 (87%) Prophage 3-bearing strains tested. Its linear dsDNA genome contains 63,343 bp, with a GC content of 50.2%. MQM1 genome can encode 88 proteins and 8 tRNAs, while no integrase or transposase-encoding genes were found. This podophage has an icosahedral capsid and a non-contractile short tail. We suggest that MQM1 may be a good addition to future phage cocktails against furunculosis to resolve the Prophage 3-resistance issue.