Inclusion Criteria:  Male or female ≥18 to <85 years of age. Ongoing diagnosis of diabetes. Have undergone or are scheduled to undergo surgical debridement for DFO as part of Standard of Care, with the associated bone culture positive for S. aureus and with the associated histology results consistent with the diagnosis of DFO. Meet defined study ulcer requirements as defined in the protocol  Exclusion Criteria:  Healing of the ulcer by more than 30% between screening and randomization. Evidence of sinus tract. Suspicion of neoplasm associated with the study ulcer or any non-study diabetic ulcer independent of biopsy result. Presence of erythema ≥4 cm at the study ulcer site. Presence of any cellulitis not localized to the study ulcer. Indwelling hardware at the site of the DFO. Body mass index of >40 or weight <50 kg. Presence of leg ulcer(s), regardless of limb. Abnormal liver function tests HbA1c value of more than 12% Any other clinically significant or severe disease that in the judgment of the investigator makes the patient unfit for the study or likely to withdraw prematurely from the study, or that could jeopardize the safety of the patient or confound the results of the study. Known allergy to phage products. Pregnant and/or breastfeeding. Immunocompromised at screening in the judgment of the investigator. Taking any systemic or topical antibacterial antibiotic within 2 weeks prior to the start of study treatment, for a condition other than Diabetic Foot Infection and DFO. Taking any antiviral medication within 2 weeks prior to the start of study treatment and up through the last administration of study treatment. Taking and/or receiving any therapies for the study ulcer that are not considered to be SOC. Participating in another clinical trial within 4 weeks prior to screening. Inability to obtain or provide informed consent or adhere to the protocol in the judgment of the investigator.