This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Capnocytophyga is best characterized as 
Select and explain. 
A. A Gram-negative pleomorphic rod that can cause endocarditis, B. The causative agent of trench fever, C. A Gram-negative rod, fusiform-shaped, that is associated with periodontal disease but may cause sepsis, D. The causative agent of rat-bite fever
C: A Gram-negative rod, fusiform-shaped, that is associated with periodontal disease but may cause sepsis
Answer: C: A Gram-negative rod, fusiform-shaped, that is associated with periodontal disease but may cause sepsis 
Explanation: While admittedly rare in human medicine, the bacteria referred to should be appreciated for their role in human disease. Branhamella is a Gram-negative diplococcus. It has recently been renamed Moraxella catarrhalis. While it is a member of the normal flora, it may cause severe upper and lower respiratory tract infection, particularly in the immunosuppressed patient. Most isolates produce b-lactamase and are resistant to penicillin. Cardiobacterium, as the name implies, causes endocarditis. This small Gram-negative pleomorphic rod may take a few days to grow. Infection is usually endogenous in that Cardiobacterium is part of the normal flora of the gut. Capnocytophaga grows best in a carbon dioxide atmosphere as the name implies. It is isolated frequently from patients with periodontal disease but may also cause septicemia in susceptible patients. Rat-bite fever is caused by Spirillum and the agent of cat scratch disease is B. henselae.