Laboratory maintenance of Coxiella burnetii

Coxiella burnetii, an obligate intracellular Gram-negative bacterium, is the agent of Q fever, a self-limited flu-like illness that may also present as chronic endocarditis. The ability to persist in the environment at a low infectious dose in aerosols resulted in the classification of C. burnetii as a BSL-3 select agent. Routine propagation of this agent is in embryonated eggs or tissue culture. Purification from host tissues includes multiple differential centrifugations to separate bacteria from host material. Infection of host cells is routinely verified microscopically by using Gimenez stain, fluorescent dyes, or immunofluorescence antibody (IFA) staining. Identification of C. burnetii DNA in host material is measured by PCR. Quantification of purified C. burnetii is accomplished through conversion of optical density to dry weight or, more precisely, by RT-PCR to determine genome equivalents. Serum antibody titer to C. burnetii is determined by microagglutination assay or ELISA.