It belongs to the HACEK group of fastidious bacteria that are present in normal oropharyngeal flora and can develop into infective endocarditis.
Cardiobacterium species are Gram-negative, pleomorphic rod-shaped bacteria that are catalase-negative and oxidase-positive.
When compared morphologically, the two Cardiobacterium species are indistinguishable in culture and Gram stain, however the two differ in growth patterns: C. valvarum is more fastidious than C. hominis, and is non-hemolytic.
The Cardiobacterium species are broadly susceptible to beta-lactam, trimethoprim-sulfamethoxazole, fluoroquinolones, and aztreonam.
Current clinical guidelines recommend that C. valvarum infection be treated with a 4-week course of ceftriaxone or ciprofloxacin.