Isolation of a new myovirus, phiIPLA-LAVI, with potential for biocontrol application in the dairy industry

Effective biocontrol of Staphylococcus aureus in foods requires the use of new antimicrobials, such as bacteriophages, especially due to the emergence of multidrug-resistant strains. This study reports the isolation of a new myovirus, phiIPLA-LAVI, from a sewage sample. Despite its specificity against S. aureus, the host range of this phage is quite broad within its target species, infecting 83.7 % of the 43 strains tested. phiIPLA-LAVI has a circular genome, approximately 132,180 bp in size, and belongs to the Herelleviridae family, representing a new species within the Silviavirus genus. Furthermore, no genes involved in lysogeny, virulence or antibiotic resistance were detected, making it potentially safe to use in phage therapy or biocontrol. Compared to other Staphylococcus phages, phiIPLA-LAVI exhibited a similar burst size (25 PFU/infected cell), but a shorter infection cycle (25 min), suggesting a faster antimicrobial action. Additionally, this phage displayed stability at temperatures of up to 60 °C and pH values between 4 and 11. phiIPLA-LAVI demonstrated the ability to kill cells in dairy matrices like milk, enzymatically-coagulated cheese and acid-coagulated cheese. The latter would be facilitated by its high stability at the pH values found during fermentation (between 4 and 7). This makes phiIPLA-LAVI more suitable than those staphylophages (like phiIPLA-RODI) that are significantly inactivated at a pH of 4. Besides reducing the S. aureus population in milk during cheese manufacturing, this phage displayed limited, but promising, potential for preventing and eliminating biofilms grown in milk, thereby reducing the ability of this pathogen to persist on dairy surfaces.