Long, thin gram-negative rods tapered at the ends are most characteristic of which genus?

Long, thin gram-negative rods tapered at the ends are most characteristic of which genus?

• A. Bacteroides
• B. Fusobacterium
• C. Porphyromonas
• D. Prevotella

Answer: (B)

Long, thin gram-negative rods with tapered ends are the hallmark of Fusobacterium. This spindle-shaped (fusiform) appearance, with pointed ends, is distinctive for this genus and reflects its morphology as anaerobic, non-spore-forming bacteria commonly found in the oral cavity and linked to dental and oropharyngeal infections. While the other genera are also gram-negative anaerobes, they do not consistently present with the same tapered, fusiform rod shape, making Fusobacterium the best match for this description.

Long, thin gram-negative rods with tapered ends are the hallmark of Fusobacterium. This spindle-shaped (fusiform) appearance, with pointed ends, is distinctive for this genus and reflects its morphology as anaerobic, non-spore-forming bacteria commonly found in the oral cavity and linked to dental and oropharyngeal infections. While the other genera are also gram-negative anaerobes, they do not consistently present with the same tapered, fusiform rod shape, making Fusobacterium the best match for this description.