Which statement describes the intracellular localization of C. burnetii?

• A. It is an extracellular bacterium
• B. It resides primarily in lymph nodes
• C. It survives intracellularly in monocytes
• D. It is a respiratory virus

Answer: (C)

Coxiella burnetii is an obligate intracellular bacterium, so its localization inside the host is defined by its need to live and replicate within cells. After inhalation, it infects alveolar macrophages and circulating monocytes and survives inside the acidified phagolysosome of these cells. This intracellular niche protects it from extracellular defenses and supports dissemination via infected monocytes to other tissues. Because of this intracellular lifestyle, the statement describing survival inside monocytes best captures its localization. It is not an extracellular microbe, not a virus, and its primary niche isn’t restricted to lymph nodes.