Host cell-free growth of the Q fever bacterium Coxiella burnetii

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 11; pp. 4430 - 4434
• Main Authors: Omsland, Anders, Cockrell, Diane C, Howe, Dale, Fischer, Elizabeth R, Virtaneva, Kimmo, Sturdevant, Daniel E, Porcella, Stephen F, Heinzen, Robert A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 17-03-2009; National Acad Sciences
• Subjects: Amino acids; Animals; Bacteria; Bacteriological Techniques; Biological Sciences; Cell culture; Cell culture techniques; Cell growth; Cell-Free System; Cercopithecus aethiops; Coxiella burnetii; Coxiella burnetii - growth & development; Coxiella burnetii - metabolism; Culture Media; Cultured cells; Fever; Genomics; Metabolism; Metabolomics; Oxygen; Pathogens; Q fever; Q Fever - microbiology; Vero Cells
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0812074106

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 log₁₀) 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.