Metabolism Studies on the Brucella Group. II. The Fermentation of Monosaccharides.

It was generally believed that members of the Brucella group lack the power to ferment the common sugars until McAlpine and Slanetz 1 showed that all the varieties except the bovine abortus strains are able partly to decompose and utilize the available glucose in the medium. Meyer and Eddie 2 failed to find any definite correlation between the type of Brucella and glucose utilization. More recently Coleman and coworkers, 3 Mallardo, 4 and Duncan and Whitby 5 found slight acid changes in arabinose, xylose, galactose and levulose. However, the degree of acid production varied with the different strains and could not be correlated with the origin of the cultures.

Since preliminary tests indicated that the chlorphenol red indicator used by Coleman and coworkers is reduced by certain Brucella strains it appeared desirable to test the fermentative properties of a large series of strains by the following procedure: A 1% filtered beef infusion rendered sugar-free by the action of B. saccharolyte, 0.5% NaCl, 0.2% agar adjusted to a pH 6.9 was mixed with 1% filtered goat serum and 1% carbohydrate (filtered solutions), tubed in 3.5 cc. amounts, tested for sterility and inoculated with a uniform sized loopful of a slant culture suspended in saline. The tubes were held at 37° C. and the pH of the cultures determined with brom thymol blue according to the method of Clark, 6 on the 3rd, 7th, 10th, 14th, and 21st day of incubation. Changes in the reaction became perceptible in 3 to 7 days, the maximum intensity being reached in 10 to 21 days. Duplicate determinations were made on 194 strains from host origins in 15 countries of the world.

The semi-solid consistency of the medium favored the growth of the bacteria and the low buffer content permitted a rapid change in the H-ion concentration.