The Bacteriological Determination of Lactose in Blood.

Abstract

The difference between the action of B. coli communis and B. paratyphosus upon lactose, as contrasted with the similarity of the effect of these organisms upon all other common sugars has been known for a long time, and has been utilized by Castellani for showing the presence of lactose in urine. In the work reported in the present communication this fermentation reaction is applied to the demonstration and approximate determination of that sugar in blood. Plasma was precipitated by the method of Folin and Wu, brought to a slight degree of alkalinity by the addition of a phosphate buffer mixture, and sterilized in a boiling water bath. It was then divided into 2 parts, one of which was inoculated with B. coli communis, and the other with B. paratyphosus A. Both preparations were incubated for 24 hours at body temperature. They were then again immersed in a boiling water bath, the organisms removed by centrifugalization, and the residual reducing power determined by a method already described. In a great majority of the blood samples taken before breakfast, identical results, within the limits of the colorimetric method, were obtained with the two organisms. Lactose added to blood to give concentrations of 0.1 to 0.005% was completely removed by B. coli communis and was not affected by B. paratyphosus A. Glucose, levulose, maltose, and galactose added to blood to give concentrations of 0.1% additional sugar were completely destroyed by both organisms. In spite of these experiments it cannot be positively stated that a difference between the reducing power of filtrate inoculated with the two organisms is due to lactose, but it seems very probable that this will be true in a great majority of instances.