title: Host cell-free growth of the Q fever bacterium Coxiella burnetii.
abstract: The inability to propagate obligate intracellular pathogens under axenic (host cell-free) culture conditions imposes severe experimental constraints that have negatively impacted progress in understanding pathogen virulence and disease mechanisms. Coxiella burnetii, the causative agent of human Q (Query) fever, is an obligate intracellular bacterial pathogen that replicates exclusively in an acidified, lysosome-like vacuole. To define conditions that support C. burnetii growth, we systematically evaluated the organism's metabolic requirements using expression microarrays, genomic reconstruction, and metabolite typing. This led to development of a complex nutrient medium that supported substantial growth (approximately 3 log(10)) of C. burnetii in a 2.5% oxygen environment. Importantly, axenically grown C. burnetii were highly infectious for Vero cells and exhibited developmental forms characteristic of in vivo grown organisms. Axenic cultivation of C. burnetii will facilitate studies of the organism's pathogenesis and genetics and aid development of Q fever preventatives such as an effective subunit vaccine. Furthermore, the systematic approach used here may be broadly applicable to development of axenic media that support growth of other medically important obligate intracellular pathogens.
authors.affiliation: Coxiella Pathogenesis Section, Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
authors.forename: Anders
authors.initials: A
authors.lastname: Omsland
authors.forename: Diane C
authors.initials: DC
authors.lastname: Cockrell
authors.forename: Dale
authors.initials: D
authors.lastname: Howe
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Fischer
authors.forename: Kimmo
authors.initials: K
authors.lastname: Virtaneva
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Sturdevant
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Porcella
authors.forename: Robert A
authors.initials: RA
authors.lastname: Heinzen
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D002474:Cell-Free System; D002522:Chlorocebus aethiops; D016997:Coxiella burnetii / Q000254:growth & development* / Q000378:metabolism; D003470:Culture Media; D023281:Genomics; D055432:Metabolomics; D011778:Q Fever / Q000382:microbiology*; D014709:Vero Cells
chemical_list: D003470:Culture Media