<b><i>Coxiella burnetii</i></b> - Pathogenic Agent of Q (Query) Fever

1.1.1 Structure C. burnetii is a member of the family of the Coxiellaceae bacteria and replicates intracellularly in cells of different species. Phylogenetically related bacteria include Legionellaceae, Francisellaceae, Pseudomonaceae, and other Gammaproteobacteria. Coxiella are small Gram-negative, pleomorphic, coccoid bacteria with a size of 0.2–1.0 m. They occur in 3 different forms: small cells (small cell variant, SCV) which are highly infectious, large cells (large cell variant, LCV) which develop also in cell culture, as well as spore-like particles (SLP) which are infectious and very robust to environmental conditions. Dependent on the host system, Coxiella undergoes a phase variation during growth [12]. In mammalian cells, bacteria grow as LCV, and form spore-like particles and 2 different antigenic forms described as Phase I and II.