The Producer and Biological Activities of SO-75R1, a New Mutactimycin Group Antibiotic [corrected]

The producer of SO-75R1, a new anthracycline group antibiotic was identified as Nocardia brasiliensis. SO-75R1 was active against Gram-positive bacteria, but not active against Gram-negative bacteria or fungi. All tested Nocardia brasiliensis strains as well as the producer itself were resistant to SO-75R1, although four other pathogenic Nocardia, i.e. N. asteroides, N. nova, N. farcinica and N. otitidiscaviarum were sensitive [corrected].