A Method for the Quantitative Determination of Fecal Bacteria

From results of which the foregoing data form a part, it appears that the amount of bacterial nitrogen in the feces is a valuable index to intestinal conditions, and the method herein described is a simple and satisfactory one for making this determination. It involves three serial centrifugalizations of a two gram sample of the fresh feces brought into suspension in 0.2 per cent. hydrochloric acid. The bacterial suspension finally obtained is concentrated and extracted by alcohol, and nitrogen is determined in the precipitated material. The complete data on a given stool can be obtained in about five days, and one operator can take care of three or four stools in duplicate in one day. On an absolutely uniform diet of simple and easily digested food during a period of three to four weeks, the average amount of bacterial nitrogen in two subjects was found to be 53.9 per cent. of the total fecal nitrogen, and this percentage, though higher than that obtained by workers heretofore, is probably more nearly a true value for bacterial nitrogen, because no ether extraction was employed. The average daily amount of dry bacteria, calculated on the basis of the nitrogen values, is 8.27 grams.