Experimental infection of guinea-pigs with atypical and dysgonic strains of microsporum canis.

Pathogenicity tests with one dysgonic and six atypical strains of Microsporum canis were carried out on guinea-pigs. Five of the atypical strains were laboratory mutants from dysgonic strains isolated from living hosts. As sporulation and viability varied greatly between the strains, inocula consisted of suspensions of fungal fragments of known viable count. When a sufficiently active inoculum was used, lesions and fluorescent hairs were induced in the guinea-pigs by all but one of the strains tested. In each case the strain inoculated was reisolated from the lesions in pure culture. The significance of the results is discussed in the light of the unusual nature and origin of the strains.