Nocardia are aerobic actinomycetes that are ubiquitous in thesoil, decaying organic matter, and water.
The genus Nocardia has been classified into 10 species on the basis of phylogenetic analysis of 16S rRNA. These species can be differ-entiated on the basis of biochemical reactions. Nocardia asteroides, Nocardia brasiliensis, Nocardia otitidiscaviarum, and Nocardia farcinica are the species frequently associated with human infections. Nocardia species also cause infection in animals, including bovinemastitis in cattle and nocardiosis in horses.
Nocardia infection was first described by French veterinarianEdmund Nocard in a pulmonary and cutaneous disease of cattle. The genus Nocardia is named so in honor of the scientist.