Identification of the causative agents and the epidemiology of porcine brucellosis.

Brucella organisms that had been isolated from swine or from human beings exposed to infected swine, and that had been previously identified as members of the species Br. melitensis, were examined for their oxidative metabolism, for their growth patterns on media containing basic fuchsin and thionin, and for their hydrogen sulfide production. These organisms displayed the oxidative metabolic pattern that characterizes and identifies the members of the species Br. suis. They also are identical to Br. suis, type 1, in their tolerance to increased concentrations of thionin in the growth media. They are similar to Br. suis, type 2, in their inability to produce hydrogen sulfide, and share with other members of the species Br. suis the characteristic preference for a porcine host. These findings are evidence that these organisms are not Br. melitensis but are a biotype of Br. suis. Their correct identification is important to understanding the epidemiology of brucellosis.