Hyperkeratosis-associated coryneform infection in severe combined immunodeficient mice.

Hyperkeratosis-associated coryneform (HAC) is a coryneform bacterium, with a biochemical profile similar to Corynebacterium bovis, that causes hyperkeratotic dermatitis in athymic nude mice. In the present study 28 severe combined immunodeficient (SCID) mice coming from six different animal facilities were submitted for bacteriological and pathological examination. HAC was isolated from 10 SCID mice belonging to two of these facilities. Two of the HAC-infected mice showed macroscopical lesions consisting in large alopecic areas, with small white flakes, involving the dorsum, flanks, neck and cheeks. Histologically, the skin of these animals was characterized by diffuse acanthosis and hyperkeratosis. In the other eight HAC-infected SCID mice no macroscopical lesions were observed but focal areas of minimal to mild acanthosis were histologically detected in five cases. These results suggest that HAC can infect SCID mice inducing skin lesions similar, although generally less severe, to those observed in nude mice with hyperkeratotic dermatitis. Our results pointed out that SCID mice may play an important role in the epidemiology of hyperkeratotic dermatitis of athymic nude mice.