There are a few species of Mycobacterium that affects aquatic frogs in the genera Xenopus, Hymenochirus and Silurana: Mycobacterium fortuitum, M. marinum, M. piscium and M.chelone.
There is an interesting article about a new species of Mycobacterium and Xenopus in
Godfrey, D; Williamson, H.; Silverman, J.; Small, P.L.C. Newly identified Mycobacterium species in a Xenopus laevis colony.Comparative Medicine. 2007; 57 (1): 97-104. ISSN: 1532-0820
Hopefully, the disease will not affect your frogs. I understand that it has a high mortality rate.