Cytotoxic activity of Propionibacterium acnes and other skin organisms

Culture supernatants from four species of skin micro-organisms were tested against VERO (monkey kidney cells) and skin fibroblasts for cytotoxic activity. Cytotoxic activity was produced by the three species of Propionibacterium tested (P. acnes, P. avidum and P. granulosum), and this activity was highest when cultures were grown in the presence of glucose. In contrast, Staphylococcus epidermidis was devoid of cytotoxic activity whether grown in the presence of glucose or not. The agent responsible for the cytotoxic activity was heat stable, of low molecular weight and removable from supernatants by ether extraction. These properties, coupled with the finding that the levels of cytotoxicity are directly proportional to the concentrations of propionate measured in samples, suggests that propionate is the agent responsible for the cytotoxicity of the culture supernatants. Pure propionate and the salts of other carboxylic acids (CI to C5) were tested at the same concentrations and showed different degrees of cytotoxicity depending on their chain length. Propionate may have an important role in the aetiology of the disease acne vulgaris.