Figure 3

Monsomic and disomic melanin variants differ in their virulence in a mouse inhalation model but show similar fungal loads in brain and lung tissue. (A) Three female BALB/c mice were inoculated intranasally with each of the strains indicated, and the survival of the mice was monitored (left graph). The strain H99 was the most virulent, WM626 did not cause illness during the experiment, and the white (disomy) variants showed reduced virulence compared with CBS7779 and the black variants. Ten female BALB/c mice were also challenged by intranasal inoculation with cells of either the CBS7779 strain or the black or white variants. The survival of the mice was monitored (center graph). The white (disomy) strains showed a difference in virulence from the black strains and from the parental CBS7779 strain. The data on the virulence of the white and black strains was combined, and the white strains showed less virulence than the black strains by the log rank test (P < 0.001) (right graph). (B) Examination of the fungal load in lung (a) and brain (b) tissue from the mice infected in (A) with the white or black melanin variants, or with the original CBS7779 strain. The organs from each of the ten mice per inoculated strain were harvested and analyzed for fungal burden. Serial dilutions of the homogenates were plated on Sabouraud dextrose agar plates, and colony-forming units were counted after incubation for 48 h at 30°C. Each dot indicates the result for a single mouse.