Invasive Fusarium oxysporum infection mimicking recalcitrant bacterial cellulitis in a diabetic foot ulcer.

Diabetic foot ulcers are predominantly attributed to bacterial aetiologies, but invasive fungal infections are an increasingly recognised opportunistic threat in immunocompromised patients. We present the case of a male farmer in his 30s with uncontrolled diabetes who developed a worsening necrotic ulcer on the left tibia following agricultural trauma. Despite treatment with broad-spectrum antibiotics, the wound deteriorated, exhibiting a central black eschar. Deep tissue biopsy revealed hyaline septate hyphae and fungal culture confirmed Fusarium oxysporum, identified by characteristic banana-shaped macroconidia. Management required a multimodal limb-salvage approach involving strict glycaemic control, dual antifungal therapy with liposomal amphotericin B and voriconazole and aggressive serial surgical debridement. Complete healing was achieved after 5 months without amputation. This case highlights the importance of suspecting fungal aetiology in antibiotic-refractory diabetic wounds, particularly in patients with occupational soil exposure.