MICROBIOLOGY

• 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
    • Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens and Kingella species
• 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.