Influence of pH on vaginal discharges.

The fluid content of the vagina is derived solely from: (1) Mucus secretions of the cervical columnar cells. (2) Transudation through the vaginal walls. (3) Vulval secretions from sebaceous and sweat glands. (4) Bartholin's glands, which are said to produce an "acid mucus secretion". Vaginal acidity is thought to depend on the presence and amount of lactic acid formed by the action of Doderlein's bacilli on the glycogen of the epithelial cells lining the vagina. Most pathogenic bacteria have a fairly restricted pH range and grow best at a pH of about 7-5. This may be a reflection of the fact that mammalian tissue and blood have a pH of this order. For example, the pneumococcus has an optimal pH of 7-8 and a growth range of 7-3 to 8-3. Commensal and saprophytic bacteria have a much wider growth range. E. coli has an optimum pH of 6-5 but a growth range of 4-4 to 7-8. Yeasts and fungi generally have an optimum acid pH and may grow at a pH of 2 and lower (Stephenson, 1949). Many of the published data on the pH effects on growth are vitiated because they take into account only the initial pH of the reaction, and also because of inaccurate readings due to inadequate or poorly-handled equipment. The pH changes so rapidly that the final pH of a reaction may be far removed from that at the start especially where fermentable carbohydrates are present. The reaction at which an organism is grown profoundly affects its enzyme make up; thus, although E. coli will grow at pH 4-5 to 9 (Gale and Epps, 1942), its optimal growth is strictly governed by the pH of optimal activity of the enzymes concerned with nitrogen metabolism * (Gale, 1940). Thus, measurement of oxidation reduction potential would be a more accurate reflection of the state of affairs than would pH. For practical purposes in clinical studies, accurately determined pH values taken under constant conditions have been taken as an acceptable standard of measurement in relation to bacterial, fungal, and protozool activity.