A simple method for the extraction of polysaccharide B from Brucella cells for use in the radial immunodiffusion test diagnosis of bovine brucellosis.

In order to extract the polysaccharide B of brucella used in Radial Immunodiffusion test (RID) for detection of infected cattle, a quick, simple and safe method is proposed. It consists of using phenol killed cells of B. melitensis 16 M known to produce polysaccharide B. After autoclaving brucella cells resuspended in saline, the cells are separated by centrifugation and the polysaccharide B is obtained by two successive ethanol precipitations of the supernatant. Comparison of the results of RID tests carried out with the polysaccharide extract of B. melitensis 16 M (rapid method) and 231 sera of infected cattle shows the validity of this method of preparation. Differences in yield (1.5% for the second precipitate against 0.5% for the polysaccharide-reference and in optimum dose used the reaction (10 microgram against 200 microgram) show that as many as 60 times more RID tests can be made with the polysaccharide obtained by rapid method.