Influence of Broth Cultures and Media upon the Self-Disinfection of the Skin.

Abstract

Arnold, Gustafson, Hull, Montgomery and Singer 1 reported upon the disappearance of viable bacteria from the skin when applied in 1:200 saline dilution. This suspension was chosen after varying concentrations had been applied to the skin. Pease, and Himebaugh 2 reported some observations using undiluted broth cultures of bacteria under certain conditions. These workers overloaded the skin with the foreign solids in the broth. The air drying of the skin causes a concentration of the protein and other materials in the broth upon the skin and delays its self-disinfecting power. The undiluted 24-hour-old broth cultures contain more bacteria than the skin can remove in 15 minutes, but the foreign substances covering the cornified layer are more important in the reaction than the concentrations of the bacteria.

The middle finger of both hands was submerged in the various fluid media indicated in the table. Immediately after removal the palmar surface of one finger was pressed against the surface of a sterile agar plate and smeared with a bent glass spreader. After holding the finger of the other hand free and allowing it to dry for 15 minutes, the same procedure was followed. The first culture was taken as the initial contact dose. Healthy subjects must be used for these experiments. If female subjects are used, care must be taken to avoid certain periods during the menstrual cycle, inasmuch as the disinfecting power of the skin can vary 10 to 15% at times. The skin of diabetic patients has approximately half of the disinfecting power of normal skin.

Care must be exercised in testing the physiological variations in self-disinfecting power of the skin to avoid placing a layer of foreign material over the cornified epithelium and prevent contact of bacteria with this layer.