BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is identified as one of the main drug-resistant pathogens, increasing the risk of no antibiotic availability in clinical settings and necessitating the urgent search for alternative antibacterial treatments. Phage therapy has been proposed as a therapeutic approach for bacterial infections, offering numerous advantages and broad application prospects. However, the efficacy of phage therapy in treating drug-resistant infections in humans remains uncertain. Given the current advances in phage therapy and the grim situation posed by MRSA infections, the application of lytic bacteriophages with wide-spectrum activity to treat difficult MRSA infections is proposed. OBJECTIVE: The objective is to isolate, purify, and screen lytic bacteriophages targeting MRSA from the environment and to assess their efficacy and safety through in vitro and in vivo experiments, with the aim of providing another therapy for MRSA infection. METHODS: Firstly, representative MRSA strains were selected, and their corresponding phages were isolated and purified from hospital sewage. Secondly, the isolated phages were screened to identify lytic bacteriophages with broad-spectrum activity, and their biological characteristics were analyzed. Thirdly, a systemic infection mouse model was established to evaluate the efficacy and safety of phage MSP15 against MRSA infection. RESULTS: In this study, Staphylococcus aureus Phage MSP15, a lytic bacteriophage with broad-spectrum activity targeting MRSA, was successfully isolated, purified and screened. Furthermore, in the systemic infection mouse model, administration of phage MSP15 led to prolonged survival time of MRSA-infected mice. A 100% survival rate was observed in infected mice with both immediate and delayed administration of high doses of phage MSP15 (MOI = 1), although efficacy may potentially be reduced with delayed treatment compared to immediate treatment. Additionally, an immune response was induced by phage MSP15, resulting in the production of IgG against phage MSP15, while no adverse events such as changes in core body temperature, allergic reactions, or other adverse effects were observed in mice. CONCLUSION: Lytic bacteriophages with a wide spectrum can become an auxiliary approach for treating MRSA infection.