Introduction: Diabetic foot ulcers (DFUs) complicated by polymicrobial infection and antibiotic resistance present significant management challenges, especially in patients with drug allergies that limit systemic options. This case describes the use of a customized, culture-directed topical antibiotic formulation in a patient with multiple drug allergies and a multidrug-resistant diabetic foot ulcer, resulting in substantial wound improvement and avoidance of systemic complications.
Methods: A 60-year-old female with diabetes, rheumatoid arthritis, peripheral neuropathy, lymphedema, and tobacco use developed a full-thickness plantar ulcer on the left great toe following thermal injury. The wound was initially treated with Betadine and oral doxycycline but worsened. PCR culture revealed a heavy polymicrobial burden with resistance to beta-lactams, macrolides, and tetracycline. Noting the patient’s allergies to penicillin and sulfa, a customized topical solution containing gentamicin and metronidazole was initiated alongside systemic levofloxacin and omadacycline. A subsequent culture showing Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli prompted a therapeutic change to a saline-based spray with linezolid and meropenem.
Results: Over a four-month period, the wound area decreased from 23.5 cm² to 3.9 cm², with resolution of drainage and progressive granulation. The patient tolerated all topical therapies without adverse events. Systemic antibiotic use was limited to short courses guided by culture results.
Discussion: This case demonstrates the successful use of targeted, compounded topical antibiotic therapy in the management of a multidrug-resistant, polymicrobial DFU in a patient with limited systemic treatment options. Culture-directed topical therapy provided effective local antimicrobial coverage, reduced wound size, and supported healing without adverse effects. These findings support the consideration of personalized topical antimicrobial formulations as adjunctive therapy in complex diabetic wounds, particularly when systemic antibiotic use is restricted by allergy and/or resistance.
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