Brucella species — Key Characteristics
Brucella is the most commonly reported agent of laboratory-associated infection. It is a virulent, highly infectious organism. Once this organism is suspected on the basis of clinical and/or laboratory information, do not perform additional testing. Send the isolate to the South Dakota State Laboratory for identification.
- Slow growing organisms.
- Faintly staining gram-negative coccobacillus.
- Punctate (minute spots) colonies on sheep blood agar.
- Catalase positive.
- Oxidase positive.
- Urease positive. (May be positive within 1 hour. If not, read at 24 and 48 hours.)
Identification Pitfalls to Avoid
- May be confused with Haemophilus - does not require X/Vfactors.
- Consider the possibility that an organism with characteristics similar to Brucella which is oxidase and urease negative may be Francisella tularensis.
- Brucella isolates may be misidentified by commercially available identification systems, often as Psychrobacter phenylpyruvicus (formerly Moraxella phenylpyruvica).
Look-a-likes (Other OX=/Ur+/GN/Oxidisers)
The pink tube on the left is a positive urease test.