Coxiella burnetii (Q Fever)

What disease is caused by Coxiella burnetii?

Q fever.

How does Coxiella burnetii stain, and what is its morphology?

It does not stain with Gram stain (use Gimenez instead) and is a pleomorphic coccobacillus.

Where does Coxiella burnetii specifically grow within host cells?

Inside cytoplasmic vacuoles (specifically acidic phagolysosomes).

How is Coxiella burnetii uniquely resistant compared to other rickettsiae?

It is resistant to heat, drying, and sunlight, surviving for months in dried feces or milk.

What structural feature is thought to contribute to the environmental persistence of C. burnetii?

The formation of endospore-like structures.

How is Q fever primarily transmitted to humans?

Inhalation of aerosols from infected animal products (placentas, feces, urine, or milk).

What are the two antigenic forms of C. burnetii LPS?

Phase 1 (virulent, found in humans/animals) and Phase 2 (avirulent, occurs after serial lab passage).

Higher antibody titers to Phase 1 than Phase 2 antigens indicate which stage of Q fever?

Chronic Q fever.

What is the most common clinical manifestation of chronic Q fever?

Infective endocarditis (typically in patients with pre-existing valve abnormalities).

What is the drug of choice for acute Q fever?

Doxycycline.

What combination therapy is used for chronic Q fever, and for how long?

Doxycycline and hydroxychloroquine for 18 months or longer.