Cutaneous non-tuberculous Mycobacterium ulcerans infection: A serious cause for concern

Mycobacterium ulcerans infection in horses is under-reported.

To document the successful multimodal treatment of M. ulcerans and highlight the need for further investigation due to the zoonotic nature of M. ulcerans with its related potential public health concerns.

Case report CASE DESCRIPTION: A 14-year-old gelding in the Southeastern region of Australia was diagnosed with M. ulcerans infection, initially presenting as a non-healing wound of the right flank progressing to extensive necrotic ulceration. Ziehl-Neelsen and Wade-Fite stained incisional biopsies revealed large numbers of intralesional acid-fast bacilli predominantly within the areas of necrosis, supportive of M. ulcerans infection. Real-time PCR confirmed the presence of mycobacteria. The close relationship between M. ulcerans and M. marinum meant that PCR was unable to distinguish these species. Due to the equine host and non-aquatic environment, there was a presumptive diagnosis of M. ulcerans. Multimodal treatment involving surgical debridement, biological debridement with maggots, cryosurgery, systemic antimicrobials, and analgesia was applied in a singular case of necrotising M. ulcerans. The horse had made a full recovery at the time of publication.

A single case is described.

Infection with M. ulcerans should be considered in necrotising soft-tissue lesions in regions where the organism is endemic. This case report highlights the need for specific staining and rapid PCR testing. A combination of antimicrobial therapy, surgical debridement and biological debridement with maggot therapy led to a successful outcome. In temperate or tropical regions, M. ulcerans infection should be considered as part of the differential diagnosis for necrotising, nonhealing, ulcerative lesions. A better understanding of the epidemiology and mode of transmission is essential to improve our ability to prevent, control, and potentially eliminate this pathogen.