LoVelle Beaman

Genome Sequence of the Human- and Animal-Pathogenic Strain Nocardia cyriacigeorgica GUH-2

The pathogenic strain Nocardia cyriacigeorgica GUH-2 was isolated from a fatal human nocardiosis case, and its genome was sequenced. The complete genomic sequence of this strain contains 6,194,645 bp, an average G+C content of 68.37%, and no plasmids. We also identified several protein-coding genes to which N. cyriacigeorgicas virulence can potentially be attributed.

The timing of exposure of mononuclear phagocytes to recombinant interferon gamma and recombinant tumor necrosis factor alpha alters interactions with Nocardia asteroides.

Nocardia asteroides modulates phagocyte function and grows within macrophages. Because interferon γ (IFN‐γ) and tumor necrosis factor α (TNF‐α) have been shown to activate macrophages to kill a variety of microorganisms, the effects of IFN‐γ and TNF‐α on the activation of murine macrophages and human monocytes to kill nocardiae were studied. It was found that macrophages or monocytes treated with either IFN‐γ, TNF‐α, or lipopolysaccharide as a secondary signal did not demonstrate increased microbicidal activity against N. asteroides even though these phagocytes were effective at killing the fungus Coccidioides immitis and the protozoan Toxoplasma gondii. Preincubation of phagocytes for 24 h with these compounds resulted in an enhancement of nocardial growth. In contrast, coincubation of these factors with the nocardiae and mononuclear cells during phagocytosis resulted in inhibition of nocardial growth even though this bacterium was not killed. Therefore, the specific timing of the exposure of the phagocyte in vitro to IFN‐γ or TNF‐α has a significant effect on its ability to alter nocardial growth.