Bacteriophages 6phi8, 6phi10, and 6phi13 Isolated from the Therapeutic Cocktail “Sextaphag®”

The present study provides the physicochemical and genomic characterization of three Escherichia bacteriophages (6phi8, 6phi10, and 6phi13) isolated from the commercial phage preparation “Sextaphag®”. For each bacteriophage, lytic activity against E. coli MG1655, as well as pH and thermal stability, were determined. Whole-genome sequencing was performed, followed by bioinformatic annotation and comparative genomic analysis. Bacteriophages 6phi8 and 6phi13 belong to the T4-like myoviruses with large genomes (~169 and ~171 kb, respectively), whereas 6phi10 is a T7-like podovirus with a genome size of 40.1 kb. Phage 6phi8 was assigned to the genus Mosigvirus of the family Straboviridae, 6phi13 was classified within the genus Tequatrovirus of the same family, and 6phi10 was identified as a putative novel species of the genus Berlinvirus within the family Autotranscriptaviridae. The genomes of the studied phages lack genes associated with the lysogenic cycle, as well as virulence and antibiotic resistance determinants. The results expand current knowledge of the genomic properties of phages included in therapeutic cocktails and may contribute to the development of phage preparations against infections caused by E. coli and other members of the family Enterobacteriaceae.