Coxiella burnetii RSA 493

Coxiella burnetii is an obligate intracellular, Gram-negative bacterium that replicates within the phagolysosome of the eukaryotic phagocyte. It is the etiological agent of "Q (Query) fever". It is highly infective to both humans and livestock, growing to high titer in livestock placental tissues. Thus natural infection mostly results from exposure to dust or aerosol from ruminant birth fluids. In humans, the disease manifests as an acute flu-like illness. The bacteria are found as 2 particles, both of which are infectious. The small cell variants (SCV), are responsible for the ability to survive extreme environmental conditions of desiccation, heat, sonication, and pressure. In the host, the infecting SCV develop into large cell variants (LCV) that are metabolically active. The SCV and LCV are antigenically different, but do not correspond to stationary and log-phase growth stages as has been hypothesized. Transition between SCV and LCV is accompanied by changes in the expression of surface proteins and does not involve changes in lipopolysaccharide (LPS) structure. Infectious particles have been referred to as "endospore-like", but this nomenclature is misleading because they are not structurally similar to Bacillus spores. C.burnetii (SCV form) is able to survive outside the host in soil for extended periods of time. It shows high-level resistance to UV radiation, heat, dessication, pressure and osmotic and oxidative stress. It has already been weaponized and mass-produced under various biological warfare programs (adapted in part from PubMed: 17825460).The G isolate (Q212) was acquired in Nova Scotia, Canada, in 1982 from the aortic valve of a human endocarditis patient. It disseminates less and causes less inflammatory damage than the Nine Mile isolate (COXBU) following aerosol challenge of BALB/c mice. This strain has plasmid-like sequences integrated into its chromosome. Comparison with 3 other strains, Nine Mile, Dugway and CbuK_Q154 (COBXU, COXBN and COXB1, respectively) identified very few novel genes in each isolate, in agreement with the organism's obligate intracellular lifestyle that limits opportunities for genetic exchange. (EBI Integr8)