Application of computer taxonomic techniques to the study of cutaneous propionibacteria and skin-surface lipid.

Colonisation of the forehead by propionibacteria and the composition of both free fatty acid and fatty acid of the triglyceride fraction of skin-surface lipid were studied, and the results were analysed using numerical taxonomic techniques. The density and prevalence of propionibacteria increased with age in a population of 230 children aged 5-18 years. The fatty-acid composition of casual sebum on the forehead changed with age, suggesting that the prevalence and density of organisms may be related to lipid composition. Cluster-analysis techniques revealed groups of individuals who resembled each other with respect to their triglyceride and free-fatty-acid profiles. These groups tended to consist of subjects who were of a similar age and maturity, and who were similarly colonised with propionibacteria. However, no relationship was evident between the composition of lipid and clinical acne.