SUMMARY

A total of 171 cultures of Brucella, mostly isolated in this country from milk and foetal material, was examined for sensitivity to thionin blue as well as to basic fuchsin and thionin, and for agglutination in monospecific sera. Standard strains of Brucella abortus, B. melitensis and B. suis grew in the presence of thionin blue in the concentration studied. Three groups of B. abortus were found, however, which were sensitive to thionin blue. These were: ( a) strains resembling the vaccine strain B. abortus strain 19; (b) dye sensitive strains (B. abortus type I1 Wilson), (c) a previously undescribed group. Cultures of this last group required added CO, for growth, grew on basic fuchsin and were virulent for guinea-pigs. The significance of these results is briefly discussed