The Collaborative International Dictionary
Streptomyces noursei
nystatin \nystatin\ n. [From NY state + -in, due to its discovery in New York State.] An antifungal antibiotic, extracted from fermentation broths of the soil actinomycete Streptomyces noursei and other actinomycetes; called also fungicidin. It is a polyene macrolide antibiotic, and consists of several related components. Component nystatin A1 has formula C47H75NO17.
Wikipedia
Streptomyces noursei
Streptomyces noursei is a bacterium species in the genus Streptomyces.