Targeting the Mycobacterium ulcerans cytochrome bc(1):aa(3) for the treatment of Buruli ulcer.

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a neglected tropical skin disease that is most commonly found in children from West and Central Africa. Despite the severity of the infection, therapeutic options are limited to antibiotics with severe side effects. Here, we show that M. ulcerans is susceptible to the anti-tubercular drug Q203 and related compounds targeting the respiratory cytochrome bc(1):aa(3). While the cytochrome bc(1):aa(3) is the primary terminal oxidase in Mycobacterium tuberculosis, the presence of an alternate bd-type terminal oxidase limits the bactericidal and sterilizing potency of Q203 against this bacterium. M. ulcerans strains found in Buruli ulcer patients from Africa and Australia lost all alternate terminal electron acceptors and rely exclusively on the cytochrome bc(1):aa(3) to respire. As a result, Q203 is bactericidal at low dose against M. ulcerans replicating in vitro and in mice, making the drug a promising candidate for Buruli ulcer treatment.