Pathogenicity of yeasts and algae isolated from bovine mastitis secretions in a murine model.

The pathogenicity of strains of yeasts and algae isolated from bovine mastitis secretions was evaluated in immunosuppressed mice. Strains of Candida tropicalis (n = 3) were the most pathogenic, but all strains of Geotrichum capitatum (n = 5) and the colourless alga Prototheca zopfii (n = 5) were also lethal to mice at the highest dose of 1 x 10(7) CFU per mouse. Reisolation of the inoculated micro-organisms and the occurrence of histopathological lesions within organs of mice challenged with 1 x 10(3) to 1 x 10(7) CFU per animal revealed strains of C. krusei (n = 17), C. kefyr (n = 6) and C. rugosa (n = 6) to have a moderate pathogenicity, whereas strains of C. valida (n = 1) and C. catenulata (n = 2) were weakly pathogenic and non-pathogenic respectively.