Tropical ulcer — DTM&H MCQ

Correct answer: D — Oral metronidazole and wound care with debridement

The correct answer is D, oral metronidazole and wound care with debridement. This is a classic tropical (phagedenic) ulcer, a synergistic anaerobic infection caused by fusospirochaetal organisms (Fusobacterium species plus Borrelia vincentii), occurring in malnourished, barefoot individuals in the tropics, with the described necrotic base and undermined edges being typical. Because the causative organisms are anaerobic, an anaerobicidal agent such as metronidazole is the mainstay of antimicrobial treatment, combined with debridement of necrotic slough, wound cleansing, and nutritional rehabilitation, which addresses the underlying malnutrition driving the infection. Antibiotics such as metronidazole and tetracycline are used alongside surgical debridement, which is consistent with standard management described in dermatological references for this condition. Why the other options are wrong: E. Systemic antifungal therapy for 6 months: There is no fungal pathogen here; the swabs confirm a bacterial (fusospirochaetal) aetiology, so antifungals have no role. B. Intralesional pentavalent antimonial: This is treatment for cutaneous leishmaniasis, which presents differently (painless nodular or crusted lesions without the characteristic undermined necrotic edge and without Fusobacterium/Borrelia on culture). C. Rifampicin plus clarithromycin for 8 weeks: This regimen is used for Buruli ulcer caused by Mycobacterium ulcerans, which typically has a painless, cotton-wool-like undermined edge but grows acid-fast bacilli, not Fusobacterium and Borrelia. A. Surgical excision with skin grafting: Grafting may eventually be needed for large chronic defects after the infection is controlled, but it is not first-line management and does not address the active anaerobic infection; premature grafting onto infected tissue fails. Key point: Necrotic, undermined tropical ulcers in malnourished barefoot patients growing Fusobacterium and Borrelia vincentii represent fusospirochaetal tropical ulcer, treated with metronidazole, debridement and nutritional support, not antifungals, antimonials, or mycobacterial regimens.

Reference: DermNet NZ, Tropical ulcer, clinical overview and treatment (antibiotics including metronidazole and tetracycline, with surgical debridement), https://dermnetnz.org/topics/tropical-ulcer