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

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.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2009; 106(11):4430-4. DOI: 10.1073/pnas.0812074106
Source: PubMed


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.

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    • "(Kikuchi, 2009) motivate future efforts to develop suitable growing conditions and techniques to access the uncultivable majority of bacteria. Genome analysis in particular has proven a powerful method to pinpoint nutrient and oxygen requirements for microbial growth (Kikuchi, 2009; Omsland et al., 2009). The loss of key primary metabolic pathways in Ca. "
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    • "Until recently, researchers attempting to investigate the molecular mechanisms of Coxiella pathogenesis have been restricted by the obligate intracellular nature of Coxiella. However, the advent of axenic culture conditions, using acidified citrate cysteine medium (ACCM), has transformed our capacity to examine this unique pathogen (Omsland et al., 2009). "
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    • "bacteria that are classified into the gamma subgroup of proteobac - teria ( Roux et al. , 1997 ) . Later on , the study by Omsland et al . ( 2009 ) reported that C . burnetti can be cultured on axenic ( host cell - free ) media . The sequence identity of the 16S rRNA gene among the Coxiella - like bacteria varies from species to species . When the 16S rRNA nucleotide sequences are compared with each other using C . burnetii as a reference genome , a maximal and a minimal nucleoti"
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