Pathogenicity of morphological and auxotrophic mutants of Candida albicans in experimental infections.

The relative pathogenicities of yeast and mycelial forms of Candida albicans were determined after intravenous injection of the two forms into mice. Yeast and mycelial forms of C. albicans CMI45348 were prepared in chemostat culture. Both morphological forms were pathogenic, but the histology of kidney sections always showed a mixture of the yeast and mycelial elements of the organism. Similarly, infection of mice with prototrophic strains produced a mixture of morphological forms at the site of infection. The yeast (CA2) and mycelial (hOG301) morphological mutants of C. albicans were pathogenic, and sections from the kidneys of the infected mice showed that the mutants retained their original morphological forms. These data indicate that both the yeast and mycelial forms of C. albicans can adhere, invade, and proliferate in an infected host. Auxotrophic diploid mutants were nonpathogenic. However, construction of a prototrophic tetraploid strain from two auxotrophs restored the pathogenicity of the organism.