Virulence profile of strains of Cryptococcus neoformans var. grubii evaluated by experimental infection in BALB/c mice and correlation with exoenzyme activity

To evaluate the virulence profile of strains of Cryptococcus neoformans var. grubii, 62 strains of this yeast were inoculated into BALB/c mice. It was found that 69% of the strains were significantly more lethal to the mice and were recovered from a higher percentage (60%) of the organs compared with the other 31% of the strains, which were recovered from 35% of organs tested. Those strains that provoked higher death rates were also recovered from the central nervous system at a higher rate (84%) than the less lethal strains (32%). This finding led to an investigation of the factors that enhanced the capacity for neurological infection and death of the animals. The results of this study suggested that environmental strains present different degrees of virulence. The correlation of exoenzyme production before and after inoculation and between the groups of mice indicated that exoenzyme production had no influence on differences in virulence among the strains studied.