Brucella Species

MICROBIOLOGY

• Aerobic, intracellular Gram-negative coccobacilli [Fig 1] causing brucellosis.
• Grows on various media, usually within 24-48h of inoculation.
• Zoonotic disease, the most important species for human infections:
  
  • B. abortus (cattle, buffalo)
  • B. melitensis (goat, sheep, camel)
  • B. suis (swine, wild animals)
  • B. canis (dog)
  • Less common:
    
    • B. ovis (sheep)
    • B. neotomae (desert and wood rats)
    • Three marine species also described as afflicting marine mammals (B. delphini, B. pinnipediae, B. cetaceae) have been described causing human disease.
• Most human infections are due to B. arbortus and B. melitensis.
  • There is a correlation between seroprevalence in animals and human cases.
  • Recently, several taxonomists merged the free-living, environmental Ochrobactrum species with members of the genus Brucella. However, this may cause clinical misunderstanding if these are not reported distinctively.
    • Laboratories reporting Brucella species causing human disease should make a distinction between these from non-pathogenic organisms, namely Ochrobactrum species.