Nocardia and Actinomyces

Nocardiosis is an opportunistic infectious disease caused by a ubiquitous aerobic bacterium of the genus Nocardia that can be found in the environment. These intracellular bacteria are held responsible for many infections affecting the lungs, the brain or the skin, especially in immunocompromised patients. The taxonomy of this bacterium is complex and a multilocus sequence analysis may sometimes be necessary for a correct identification. Only three complete genomes of the genus Nocardia have so far been fully sequenced and referenced which constitutes an important stage in the study of this bacterium. Actinomyces belong to the normal indigenous microflora, so that they are considered as facultative pathogens. Actinomycosis is usually associated with the breakdown of normal physical barriers, such as disruption of mucosal membranes. Actinomycosis and nocardiosis are distinct diseases that respond to very different forms of therapy. Actinomyces can be readily distinguished from Nocardia by their distinct anaerobic versus aerobic patterns of growth after isolation from a clinical sample.