1. A genus of filterable bacteria (order Rickettsiales) containing small, pleomorphic, rod-shaped or coccoid, gram-negative cells that occur intracellularly in the cytoplasm of infected cells and possibly extracellularly in infected ticks. These organisms have not been cultivated in cell-free media; they are parasitic on humans and other animals; type species is Coxiella burnetii.
See: Q fever
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