Which organism is an etiologic agent of endocarditis?

• A. Haemophilus influenzae
• B. Cardiobacterium hominis
• C. Vibrio vulnificus
• D. Legionella pneumophila

Answer: (B)

Endocarditis is commonly caused by bacteria that stick to damaged heart valves and form vegetations, with a classic group of fastidious organisms known as the HACEK group being well recognized for causing subacute endocarditis. Cardiobacterium hominis is a classic member of this group and is a typical etiologic agent because it originates from the oropharynx and tends to grow slowly in culture, matching the often indolent course of endocarditis associated with HACEK organisms. In this context, it’s the organism most characteristically linked to endocarditis among the options. By contrast, Vibrio vulnificus is mainly associated with seafood-related wound infections and septicemia, Legionella pneumophila with Legionnaires’ disease, and Haemophilus influenzae, while capable of causing various infections, is not the prototypical endocarditis agent listed here.