Micrococcus indolicus. Some biochemical properties, and the demonstration of sex antigenically different types.

A total of 274 strains of Micrococcus indolicus, 211 of which had been isolated from cases of summermastitis, 13 from other cases of mastitis in cattle, 15 from other suppurative lesions in cattle, 13 from insects, 13 from the vagina and interdigital skin of clinically healthy cows, and 9 from various suppurative lesions in swine, were studied and compared with 4 strains of anaerobic cocci of human origin, presumably representing at least 3 species closely related to Mi. indolicus: Staph. asaccharolyticus Distaso, Staph. aerogenes Schotmüller, and Staph. anaerobius Jungano. The growth characteristics of Mi. indolicus are described, and the most important biochemical criteria for its identification stated briefly (Table 1). By double diffusion-in-gel analysis 217 strains of Mi. indolicus could be divided in 6 antigenic types, designated A, B, C, D, E, and F (Figures 2, 3, 4, and 5, Tables 2, 3, 4, and 6). By the complement fixation technique no difference could be demonstrated between the 6 types (Table 5). Strains isolated from healthy cattle or from insects all belonged to antigenic types commonly found in summermastitis. Three of 9 porcine strains belonged to a type (F) hitherto not found in cattle. The 4 human strains of anaerobic cocci showed no antigenic relation to Mi. indolicus (Table 5) and differed from it in growth characteristics and in biochemical properties (Table 1). It is concluded that, as suggested by (1934) Micrococcus indolicus should be classified as a species of its own and not as a variant of Staphylococcus asaccharolyticus Distaso 1967).