Adjunctive laser-based antimicrobial photodynamic therapy using methylene blue for refractory feline sporotrichosis

Feline sporotrichosis, a potentially zoonotic fungal infection caused by Sporothrix spp., represents a therapeutic challenge, especially in refractory cases. This report describes two cases that presented with refractory cutaneous lesions to conventional systemic treatment. Both cats were initially treated with a combination of itraconazole and potassium iodide for a prolonged period, resulting only in partial improvement and persistence of cutaneous lesions. Due to the lack of complete response, antimicrobial photodynamic therapy (aPDT) was introduced as an adjuvant treatment. The protocol involved multiple sessions of aPDT using methylene blue as photosensitizer, while conventional therapy was maintained. The first cat achieved complete clinical cure after 11 sessions and the second after 10 sessions. The successful outcome in these cases demonstrates the potential of aPDT as a promising adjuvant technique in the treatment of refractory feline sporotrichosis.