Type-species of the Nocardia, a markedly acid-fast branching mycelial organism with grey-white to yellowish colonies. Associated with tuberculous-like processes in cattle.
Non-acid-fast species, colonies white, buff or crimson, but chromogenicity is unpredictable. Actinomycosis-like pus is formed in the tissues. Associated with Madura foot (tropical and subtropical areas) but this condition is also as often fungal in origin.