The bacterium Dermatophilus congolensis is the causative agent of pitted keratolysis, a skin disease. Infection occurs mainly in keratinized tissues and it is necessary for the organism to produce and excrete exoenzymes which are able to degrade keratin. We investigated the amount of keratinase liberated using Keratinazure as substrate and the fungal protease XI as standard. When compared with uninoculated samples, D. congolensis liberated significant amounts of keratinase during a 12-day incubation period with this substrate. An equivalent of 15 units of protease (keratinase) was produced by 10(7) colony-forming units of D. congolensis during a 12-day period at 37 degrees C. We consider the extracellular proteolytic activity of this bacterium to be responsible for keratinized tissues being the main sites of infection.