A new antibacterial antibiotic, designated simaomicin alpha (LL-D42067 alpha) was isolated from the fermentation broth of an actinomycete strain. Based on cultural, physiological, morphological and chemical characteristics, culture LL-D42067 was identified as a new subspecies of Actinomadura madurae. Simaomicin alpha demonstrated potent activity against Gram-positive bacteria and was active in vivo against a variety of Eimeria species causing coccidiosis in chickens.