The present invention relates to a new composition designated as AM-1042 or asukamycin. AM-1042 has an antibiotic activity upon Gram-positive bacteria and Eimeria, and its acute toxicity (LD50' ip.) in mice was 48.5 mg./kg. AM-1042 has an excellent therapeutical effect on various infectious diseases caused by a parasite of Gram-positive bacteria and Eimeria. AM-1042 has been confirmed to be distinguishable from known antibiotics such as e.g. amicetin B, azomycin and manumycin. AM-1042 is produced by fermentation of a microorganism belonging to the genus Streptomyces and capable of producing AM-1042. A composition capable of preventing and curing coccidiosis of poultry containing AM-1042 as active ingredient.
