Novel bacteriophage vB_SauH_SPJ2 against methicillin-resistant Staphylococcus aureus: Characterization and potential application in milk safety

Methicillin-resistant Staphylococcus aureus (MRSA), resistant to β-lactam antibiotics, presents critical treatment challenges. Bacteriophages (phages) are increasingly considered an alternative therapy for combating antibiotic-resistant pathogens. This study aimed to isolate and characterize a novel lytic phage targeting MRSA, evaluate its efficacy in biofilm disruption and potential as a biocontrol agent in milk. Phage vB_SauH_SPJ2 was successfully isolated and exhibited a short latent period (15 min) and high burst size (99 PFU/cell). Stability assays showed that SPJ2 remained stable across a broad range of temperatures (4–50 °C) and pH (3–12) conditions. Morphological and genomic analyses revealed that SPJ2 represented a novel species within the Silviavirus genus, belonging to the Twortvirinae subfamily of the Herelleviridae family, lacking resistance genes. SPJ2 significantly disrupted preformed biofilms of MRSA SA008 (59.05 %), MDR S. aureus SA009 (79.15 %), and S. aureus CMCC26003 (56.72 %) after 24 h, while inhibiting biofilm formation by 86.43 %, 44.56 %, and 71.38 % in a concentration-dependent manner, respectively. The SPJ2-encoded lysin may lyse bacteria and degrade extracellular polymeric substances (EPS), thereby inhibiting and removing biofilm synthesis. At a multiplicity of infection (MOI) of 1000, SPJ2 exhibited effective bactericidal activity against S. aureus at 25 °C and 4 °C. Notably, SPJ2 reduced the concentration of S. aureus in milk to undetectable levels within 6 h at 25 °C, demonstrating exceptional biocontrol potential. Statistical significance was analyzed using two-way ANOVA (p < 0.05). These findings highlight the adaptability of SPJ2 to dairy processing environments, efficacy against MRSA, and promise as a synergistic antimicrobial agent for clinical and industrial applications.