A Differential Plating Medium for Lipase-Producing Bacteria.

Abstract

A need for a differential plating medium for lipase-producing bacteria was felt when a study was begun a year and a half ago for the purpose of classifying the bacterial flora of the gastro-intestinal canal in certain diseases possibly due to bacteria present there; i. e., pellagra, sprue and pernicious anemia. Since diet has such an important bearing upon these diseases, it was decided to try as a basis for classification, in part at least, the action of the various bacteria present on certain fundamental elements of food, i. e., fats, starch, protein. This seems practicable only by means of differential plating media. The medium under discussion has been in use for more than a year and only a partial study of its possibilities has been made. However, since it might be useful to others, it was thought well to publish a description at this time. The composition of the media is as follows: Sugar free meat digest fluid, 1,000 cc.; Di-basic sodium phosphate, 5 gm.; Agar, 30 gm. Melt, clear, adjust for final pH of 7.6. Autoclave. Add 0.125 gm. nile blue sulphate in 100 cc. 25% ethyl alcohol. Tube in 6 to 7 cc. amounts in tubes already sterile. Arnold for 15 minutes. Store. To use, the agar is melted and cooled to 45°-50° C. A sterile emulsion of fat is added to about 10% volume; 0.7 cc. for 7 cc. tube. We use either cream or one of cotton seed oil made according to directions in U. S. Pharmacopeia for codliver oil except 25% more water is used than prescribed.