Mel- mutants of Wangiella dermatitidis in mice: evaluation of multiple mouse and fungal strains.

Melanin-deficient mutants of Wangiella dermatitidis were studied by comparing a spontaneous mutant (Mel 3) with the parental wild type (wt) in four strains of mice and by comparing various UV-induced mutants in a single strain of mouse. Mice were inoculated intravenously with 3 x 10(6), 1 x 10(7), 3 x 10(7) or 1 x 10(8) yeast-like cells and mortality assessed at the end of 20 days. Neuropathology was evaluated in methenamine-silver stained brain sections of the different strains of mice injected with either wt or Mel 3 (1 x 10(7) cells per mouse). In general, both fungus strain related and mouse strain related differences in mortality were observed. The DBA/2J mouse was the most susceptible to fatal infection with all fungus strains. In the other strains of mice, however, the melanin deficient mutants were significantly less virulent than the wt at a concentration of less than or equal to 3 x 10(7) cells per mouse. No obvious trend was seen in the numbers of brain lesions in different strains of mice with respect to wt vs. Mel 3. However, invasive hyphal forms did seem to be associated with virulence.