The biological stability of the genus Brucella.

The constancy of the three species of Brucella (Br. abortus, Br. suis and Br. melitensis) is discussed with regard to both the historical background and current research, and the pertinent literature is reviewed and interpreted. The authors maintain that members of the genus Brucella are not labile nor are they subject to spontaneous species alteration; stability of the recognized species is confirmed when test reactions used in speciation are standardized and controlled. Particular stress is laid on the epidemiological value of retaining the original species designations. The conclusion that Brucella species are biologically stable is substantiated by the authors' combined experience of more than 30 years in the isolation and typing of Brucella derived from a variety of sources.