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Chapter 16.12 : Q Fever—Coxiella burnetii
Coxiella burnetii is the etiologic agent of Q fever. It is a pleomorphic coccobacillus that is Gram-negative, obligately intracellular, and 0.3 to 0.7 μm long. C. burnetii is phylogenetically related to Pseudomonas, Francisella, and Legionella, within the Legionella group of the Gammaproteobacteria subdivision. It is more distantly related to Rickettsia ( 1 ). There is phase variation, similar to that in Salmon-ella, in which the lipopolysaccharide (LPS) varies chemically as either the virulent, phase I “smooth” type LPS, or the phase II “rough” LPS, associated with avirulent C. burnetii. Q fever is a zoonotic disease, especially of parturient goats, sheep, or cattle and, occasionally, domestic cats. That the infectious dose is very low, combined with properties of aerosolized contaminated dust particles being an efficient source of infection, and resistance to inactivation in the environment, makes C. burnetii a potential agent of bioterrorism. It has historically been developed for such a purpose and hence classified as a non-Tier 1 select agent by the CDC, U.S. Department of Health and Human Services. The primary purpose of this protocol is to guide the sentinel clinical laboratory in diagnostic sample collection and handling and to assist in the interpretation of serologic test results.