Metabolic characterization of Brucella strains that show conflicting identity by biochemical and serological methods.

Each of 87 strains of brucellae examined for its utilization of amino acid and carbohydrate substrates displayed a metabolic pattern that characterized it as to its species identity, irrespective of its serological and biochemical characters. Strains that displayed the metabolic pattern of Br. abortus were lysed by Brucella bacteriophage type abortus strain 3. Strains that displayed the metabolic pattern of Br. melitensis were not lysed by this phage.On this basis of identification, it is shown that there occur strains of Br. abortus that do not produce hydrogen sulfide, do not require carbon dioxide and are thionin-resistant, thereby duplicating the features generally regarded as characteristic of Br. melitensis. They can be identified by their metabolism and phage susceptibility. The distribution of Br. abortus and Br. melitensis antigens, as measured by agglutination with monospecific antisera, is also not always related to other species-identifying characteristics. Therefore, neither the serological method nor the biochemical method can be considered a reliable guide to the identification of Brucella species.