Abstract
4,000 Gram-positive, catalase-positive coccal isolates (Staphylococcus and. Micrococcus) were obtained by randomly selecting 20 colonies from face and abdomen plate cultures of 50 male and 50 female individuals. 1,888 isolates (47.2 per cent) were Micrococcus; 2,112 were Staphylococcus. A four-test scheme (anaerobic acid production from glucose, anaerobic growth in thioglycollate medium, lysostaphin sensitivity and coagulase production) permitted successful differentiation. The Micrococcus isolates were subjected to a battery of seven tests which in a preliminary study had proved to be of good differential ability (pigmentation, growth on 7.5 per cent NaCl, aerobic acid production from glucose, gelatin hydrolysis, nitrate reduction, acetoin production and arginine dihydrolase). Using these test results and a matrix-reduction computer programme (BIOTYPE) the isolates were grouped into 190 biotypes. The 190 biotypes were then reduced, by cluster analysis (GLUSTAN 1A programme), to 35 groups and subgroups of Micrococcus. 3C of the groups and subgroups were assignable to 8 recognised species of Micrococcus, namely, M. luteus, M. varians, M. lylae, M. halobius, M. kristinae, M. sedentarius. M. roseus and M, nishinomiyaensis. The remaining 5 were unidentifiable. The 100 individuals were also grouped by cluster analysis, using as data the occurrence and relative abundance on their skin of the 35 Micrococcus groups and subgroups, 4 clear groups of individuals were discerned, of broadly differing Micrococcus profiles; one contained predominantly males and another, females. 6 Micrococcus groups or subgroups appeared to be important in determining this grouping, namely, M. varians 1,2 and 3a, M. luteus 18a, M. lylae 23 and M. halobius 5a. Each of these 6 showed significant negative associations, with respect to relative abundance on the skin, with one or more of the others, suggesting mutual antagonism or the existence of different physiological skin conditions favouring some forms whilst repressing others.