Cardiobacterium spp

• C. hominis
• C. valvarum

Gram Stain

• Gram negative bacilli irregular/pleomorphic in short chains/pairs or rosettes (sometimes have bulbous ends) (facultative anaerobic)

Clinical Significance

These organisms are part of the normal flora of the upper respiratory, gastrointestinal and genitourinary tracts.

They have been associated with endocarditis (especially prosthetic valve endocarditis), septic embolization, and intra-abdominal abscesses.

Usual Susceptibility Pattern

These organisms are susceptible to most antibiotics including penicillin.

Rare beta-lactamase activity has been described.

They are also susceptible to quinolones, aminoglycosides, rifampin, and tetracyclines. Macrolide susceptibility is variable.