Brucella abortus

• Domain: Bacteria
•     Phylum: Proteobacteria
•         Class: Alphaproteobacteria
•             Order: Rhizobiales
•                 Family: Brucellaceae
•                     Genus: Brucella
•                         Species: Brucella abortus

The organism responsible for brucellosis is a small Gram-negative coccobacillus that is non-motile, non-encapsulated and non-spore-forming. In infected tissue it normally occurs singly or in small groups. The colonies are circular and 2-4 mm in diameter. Smooth colonies appear translucent, honey-coloured and bluish-green or unstained when stained with crystal violet. Rough colonies appear granular, reddish-yellow and deep violet-red when stained with crystal violet. Mucoid colonies are stringy and appear transparent, greyish and light bluish-red when stained with crystal violet.

Several commercial firms produce media suitable for the isolation of Brucella. On primary isolation it usually requires the addition of 5-10% carbon dioxide and takes 3-5 days incubation at 37° C for visible colonies to appear. Brucella abortus produces H₂S. It usually grows in the presence of basic fuchsin, but not always in the presence of thionin at standard concentrations, and is catalase and oxidase positive. It is lyzed by brucella-phages Weybridge (Wb), Firenze (Fz), Tbilisi (Tb) and Berkeley (Bk).

Each Brucella has a specific oxidative metabolic pattern that can be used to determine the ability of an isolate to utilize oxygen on various amino acid and carbohydrate substrates. Currently there are eight recognized Brucella abortus biovars (Corbel et al., 1978; Ray, 1979).

• Pest and disease transmission
• Parasitism (incl. parasitoid)