This study addresses the increasingly severe global public health challenge of antibiotic resistance, focusing on exploring phage therapy as a potential treatment strategy for multidrug-resistant bacterial skin infections. Bacteriophages, with advantages such as high specificity, low propensity for inducing resistance, and minimal side effects, have shown promise in preliminary clinical research for scenarios like chronic wound infections, demonstrating potential in reducing bacterial load and promoting healing. To this end, the study is designed as a prospective, double-blind, non-inferiority randomized controlled clinical trial, aiming to systematically evaluate the efficacy and safety of phage therapy compared to a placebo or standard treatment in patients with multidrug-resistant bacterial skin infections.

The study plans to enroll patients aged 18 to 75 years, clinically diagnosed with a skin infection and with a wound area between 4 and 225 square centimeters. The infection must not involve deep tissue and should be suitable for topical treatment. All enrolled cases must have pathogenic bacteria detected in secretions or wound samples, and these bacteria must be resistant to key antibiotics (such as carbapenems) or show poor response to antibiotic therapy despite *in vitro* sensitivity. Patients who have received systemic antibacterial treatment within 72 hours before enrollment with no significant improvement may also be included. Participants of childbearing potential must agree to use effective contraception during the study and voluntarily provide written informed consent.

Exclusion criteria primarily include: infections that can be effectively controlled by existing antimicrobials, or pathogens that are insensitive to the phage cocktail used in the study; pregnant or lactating women; patients whose infection symptoms have improved after using antimicrobials within 72 hours before enrollment; those receiving long-term or high-dose corticosteroids, immunosuppressants, chemotherapy, or other treatments that may interfere with the results; participation in other antimicrobial-related clinical trials within the past month; presence of severe wound infections (e.g., necrotizing fasciitis), chronic inflammatory skin diseases, multiple limb ulcers, non-removable implants, or gangrene; anticipated need for amputation surgery; history of clear allergic diseases, immune deficiency (including HIV positivity), mental disorders, or epilepsy; and any other condition deemed by the investigator as unsuitable for participation. These strict inclusion and exclusion criteria aim to select an appropriate target population, ensuring the scientific rigor and credibility of the study results.

Inclusion Criteria:

• (1) Aged 18 to 75 years, regardless of gender.

  (2) Clinically diagnosed with a skin infection, with an infected wound area of 4-225 cm².

  (3) The infection does not involve deep tissues, is suitable for topical treatment, and is not expected to require surgical intervention.

  (4) Pathogenic bacteria are detected in secretions or wound samples.

  (5) The pathogen is resistant to key antibiotics (such as carbapenems, etc.), or, despite being susceptible in vitro, shows poor response to antibiotic therapy.

  (6) Patients who have received systemic antibacterial therapy within 72 hours prior to enrollment without significant improvement may also be included.

  (7) Subjects of childbearing potential must agree to use effective contraception during the study period.

  (8) Voluntarily sign the informed consent form, and are willing and able to comply with the requirements of the study protocol.

Exclusion Criteria:

• (1) The infection can be effectively controlled by available antimicrobial agents, or the causative pathogen is insensitive to the phage cocktail used in this study.

  (2) Pregnant or breastfeeding women. (3) Patients who have used antimicrobial agents within 72 hours prior to enrollment and have shown improvement in infection symptoms.

  (4) Patients currently receiving prolonged or high-dose corticosteroids, immunosuppressants, chemotherapy, or other treatments that may interfere with the study results.

  (5) Patients who have participated in other clinical trials related to antimicrobial agents within the past month.

  (6) Patients with severe wound infections (e.g., necrotizing fasciitis), chronic inflammatory skin diseases, multiple limb ulcers, non-removable implants, or gangrene, among other conditions.

  (7) Patients expected to require amputation surgery. (8) Patients with a documented history of allergic disorders, immunodeficiency (including HIV positivity), mental disorders, or epilepsy.

  (9) Any other condition deemed by the investigator as unsuitable for participation in this study.

IPD (Individual Participant Data) may not be shared due to several key reasons. First, ethical and privacy restrictions are primary concerns. Informed consent forms often do not include provisions for broad public data sharing, and even anonymized data carries a risk of participant re-identification. Second, legal and data transfer agreements governing the original study frequently prohibit redistribution of raw data to third parties. Third, intellectual property and strategic considerations, such as plans for future publications, secondary analyses by the research team, or potential commercial applications, can lead researchers to retain exclusive access. Finally, technical and resource barriers, including the lack of standardized formats and the cost of preparing complex datasets for sharing, present significant practical obstacles to making IPD publicly available.