Cardiobacterium species


  • Gram-negative bacillus, aerobic, on staining, may be highly pleomorphic.
    • Part of upper respiratory human flora and occasionally on oral mucosal surfaces can be recovered in 70% of normal people.
    • Catalase-negative, oxidase-positive, indole-positive.
    • Slow-growing in traditional media, e.g., blood agar.
    • Low-virulence organism
    • Member of HACEK group that may cause endocarditis
  • Major species: Cardiobacterium hominis is the most common human pathogen species, though it remains a rare infection overall.
    • Other species:
      • C. valvarum
    • MALDI-ToF has helped improve proper microbiologic identification.
  • Traditionally, a penicillin-sensitive organism, though in recent years, beta-lactamase production has been described in some isolates.
    • Aminoglycosides and fluoroquinolones are also usually active.

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Last updated: January 18, 2023