Novel Silviavirus phages with broad-host-range activity against methicillin resistant Staphylococcus aureus from seafood: comprehending the phenotypic and genotypic variability.

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) poses significant challenges to global health, attributed to their ability to resist multiple antibiotic classes. In the current situation, phage-based biocontrol strategies offer a promising alternative, leveraging their high specificity and efficacy against multidrug-resistant bacteria. The present study reports the phenotypic and genotypic characterizations of three broad-host-range MRSA phages: φCIFT_MFB_MRSA12, φCIFT_MFB_MRSA28, and φCIFT_MFB_MRSA32 for their application in seafood safety. The phages exhibited burst sizes ranging from 75 to 107 PFU/cell and burst periods of 80-90 min. The thermal and pH stability studies indicated that φCIFT_MFB_MRSA12 exhibited the highest thermal stability (- 20 to 60 °C), while φCIFT_MFB_MRSA28 demonstrated the widest pH tolerance (pH 3-12). The genomic analysis indicated that the phages possessed linear double-stranded DNA ranging from 141,193 to 141,505 bp, with large direct terminal repeats (DTRs) of 10,893 bp and various coding and non-coding genes (group-I introns, HEARO, and RAGATH). The comparative genome analysis revealed that three phages were found to be closely related to Silviavirus phages of the Herelleviridae family and differed with respect to tail fiber proteins, Ig domain-like carbohydrate-binding domains, and certain hypothetical proteins. Interestingly, the intergenomic and phylogenetic analyses revealed that the phages belonged to a novel species. Importantly, the genomes lacked virulence factors, antimicrobial resistance genes, or lysogenic determinants, supporting their safety in biocontrol strategies. The three Silviavirus phages could be potential candidates for the biocontrol of MRSA in seafood supply chains, thereby contributing to food safety and security.