Bioterrorism Preparedness for Sentinel Laboratories

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.
• Nonhemolytic.
• 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)

• Achromobacter
• Acidovorax
• Agrobacterium
• EO-2/EO-3
• Flavobacterium
• Methylobacterium
• Psychrobacter
• Ochrobactrum
• Pseudomonas
• Riemerella
• Roseomonas
• O-2
• II-I
• Oligella

The pink tube on the left is a positive urease test.