Isolation and characterization of a novel Staphylococcus phage SPD: genomic insights and its anti-biofilm efficacy against methicillin-resistant Staphylococcus aureus.

OBJECTIVE: To isolate and characterize a novel Staphylococcus phage with activity against animal-derived methicillin-resistant Staphylococcus aureus (MRSA) infections and biofilms in Kashgar, Xinjiang. METHODS: Phage SPD was isolated through enrichment from farm wastewater, purified using the double-layer plaque assay, and characterized by using transmission electron microscopy (TEM), spot assays, growth kinetics, stability tests, and whole-genome sequencing (Illumina HiSeq). Anti-biofilm activity was evaluated via crystal violet staining. RESULTS: SPD is a virulent Podovirus characterized by an icosahedral head (~50 nm in diameter) and a short tail phage (~60 nm in length). It exhibits a broad host range (lyses 38 out of 50 tested strains, including 7 MRSA), a short latent period (~10 min), a high burst size (4,470 PFU/cell), and stability at temperatures ranging from 4 to 50 °C and pH values between 6 and 9. The 17,066 bp double-stranded DNA genome (35.1% GC content) encodes a lysin and a holin, with no virulence or antibiotic resistance genes detected. SPD effectively inhibits planktonic MRSA growth and reduces biofilm formation (>50% inhibition) as well as pre-formed biofilms (>60% clearance) in vitro. CONCLUSION: SPD represents a safe, novel Andhravirus phage with potent activity against MRSA and biofilms, offering a promising candidate for phage therapy, particularly in the Xinjiang region.