A slaughterhouse worker presents with an acute febrile illness, atypical pneumonia, and hepatitis. There is no rash, and the Weil-Felix reaction is negative. Which property distinguishes the causative agent from other members of the family Rickettsiaceae?
- A It forms a resistant spore-like small cell variant that survives outside host cells ✓
- B It is transmitted by the bite of an arthropod vector
- C It replicates freely in the cytoplasm without a vacuolar membrane
- D It possesses LPS endotoxin responsible for the rash
Correct answer: A. It forms a resistant spore-like small cell variant that survives outside host cells
Explanation
Coxiella burnetii, the agent of Q fever, undergoes phase variation and produces a highly resistant spore-like small cell variant that persists in the environment, unlike true Rickettsia species which are fragile and strictly vector-borne. It also characteristically causes pneumonia and hepatitis without any rash, and the Weil-Felix reaction is negative. Option B is wrong because transmission is by inhalation of infected aerosols, especially placental material, not arthropod bite.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.