Infections of man by Mycobacterium ulerans cause extensive necrosis of skin and subcutaneous tissue. Although the mechanism of this necrosis has not been determined, in this study we have shown that cultures of M ulcerans in vitro produce a toxin that, when inoculated into guinea pig skin, causes inflammation and necrosis. The changes in the guinea pig skin resemble those seen in naturally occurring human infections. This toxin is present in the culture filtrate, in the cytoplasmic fluid, and in the particulate fraction. It is heat-stable, active following ether extraction, and the only known toxin produced by a mycobacterium.
Krieg RE, Hockmeyer WT, Connor DH. Toxin of Mycobacterium ulceransProduction and Effects in Guinea Pig Skin. Arch Dermatol. 1974;110(5):783-788. doi:10.1001/archderm.1974.01630110073023