Abstract: A new antibiotic substance, which has been named nargenicin C.sub.1, has been isolated from fermentations of a species of the genus Nocardia. Nargenicin C.sub.1 can be used as an antibacterial agent against susceptible bacteria, especially susceptible strains of Staphylococcus aureus.

Abstract: Fermentation of a culture of Nocardia sp. ATCC 39043 produces an antibiotic complex comprising erythromycin D, 3",4"-di-O-acetylerythromycin D, 3"-O-acetyl-4"-O-propionylerythromycin D and 4"-O-acetylerythromycin D. The components are separated and are each useful in vitro and in vivo as antibacterial agents. If erythromycin D is the desired product, the esters can be hydrolyzed prior to the separation of the erythromycin D.

Abstract: Growth of cattle and swine is promoted and feed utilization efficiency increased by an improved nutrient feed containing the antibiotic of the formula ##STR1##

Abstract: Fermentation of a culture of Nocardia sp. ATCC 39043 produces an antibiotic complex comprising erythromycin D, 3",4"-di-O-acetylerythromcyin D, 3"-O-acetyl-4"-O-propionylerythromycin D and 4"-O-acetylerythromycin D. The components are separated and are each useful in vitro and in vivo as antibacterial agents. If erythromycin D is the desired product, the esters can be hydrolyzed prior to the separation of the erythromycin D.

Abstract: An antibiotic complex, consisting of two major components, has been isolated from fermentations of a new subspecies of Streptomyces albus culture. The two major components from the complex are two new macrolide antibiotics, which are active as antibacterial agents against certain gram-positive and gram-negative microorganisms.

Abstract: A new antibiotic substance, which has been named nargenicin C.sub.1, has been isolated from fermentations of a species of the genus Nocardia. Nargenicin C.sub.1 can be used as an antibacterial agent against susceptible bacteria, especially susceptible strains of Staphylococcus aureus.

Abstract: An antibiotic having the formula ##STR1## and the pharmaceutically acceptable salts thereof.

Abstract: An antibiotic complex, consisting of two major components, has been isolated from fermentations of a new subspecies of Streptomyces albus culture. The two major components from the complex are two new macrolide antibiotics, which are active as antibacterial agents against certain gram-positive and gram-negative microorganisms.

Abstract: A new acidic polycyclic ether antibiotic has the formula: ##STR1## and can be prepared by the submerged aerobic propagation in aqueous nutrient media of Streptomyces halstedii ATCC 31812. The antibiotic and its cationic salts are active against a variety of microorganisms and are effective in controlling coccidiosis, enteritis, swine dysentery and theileriosis as well as being effective in promotion of growth in poultry and ruminants.

Abstract: Antibiotics CP-54,715 and CP-54,716, identified by their analytical characteristics, are produced by fermentation of a new microbial species Catenuloplanes jaonicus in a new genus Catenuloplanes and are active against gram-positive and anaerobic infections.

Abstract: A new subspecies of Streptomyces nigellus Prokop, designated Streptomyces nigellus Prokop subsp. africanus Huang subsp. nov. ATCC 31496, when propagated under aerobic conditions in aqueous nutrient media, produces a mixture of antibiotics. One of these antibiotics is the known macrolide antibiotic cirramycin A; the ansamycin antibiotic is an analogue of protostreptovaricin and the structure has been established as 21-hydroxy, 25-demethyl, 25-methylthioprotostreptovaricin I.

Abstract: A new subspecies of Streptomyces nigellus Prokop, designated Streptomyces nigellus Prokop subsp. africanus Huang subsp. nov. ATCC 31496, when propagated under aerobic conditions in aqueous nutrient media, produces a mixture of antibiotics. One of these antibiotics is the known macrolide antibiotic cirramycin A; the ansamycin antibiotic is an analogue of protostreptovaricin and the structure has been established as 21-hydroxy, 25-demethyl, 25-methylthioprotostreptovaricin I.

Abstract: A species of Nocardia, designated Nocardia argentinensis Huang ATCC 31438, when subjected to aerobic submerged fermentation, produces an antibiotic complex containing as its major component antibiotic Compound 51,467. Methods for the recovery and purification of antibiotic Compound 51,467 and minor antibiotic components, Compounds 52,726 and 52,748, and some of their properties are outlined.

Abstract: A new species of Nocardiopsis, designated Nocardiopsis atra Huang sp. nov. ATCC 31511, when aerobically propagated in an aqueous nutrient medium, produces nocardicin A in good yield.

Abstract: A new polycyclic ether antibiotic produced by a strain of Actinomadura verrucosospora under submerged fermentation conditions is useful in controlling coccidiosis in poultry and in improving feed utilization efficiency in ruminants.

Abstract: A species of Actinoplanes, designated Actinoplanes deccanensis Parenti, Pagani and Beretta subsp. salmoneus Huang subsp. nov., ATCC 31355, when subjected to submerged aerobic fermentation, produces a new antibiotic complex. Methods for the recovery and purification of the antibiotic complex and some of the individual antibiotic components are described.

Abstract: A new polycyclic ether antibiotic produced by a strain of Streptomyces hygroscopicus under submerged fermentation conditions is useful in controlling coccidiosis in poultry and in improving feed utilization efficiency in ruminants.

Abstract: A new species of Nocardia, designated Nocardia argentinensis Huang sp. nov., when subjected to aerobic submerged fermentation, produces a mixture of new antibiotics. Methods for the recovery and purification of these antibiotics are described and some of their antimicrobial properties are outlined.

Abstract: New polycyclic ether antibiotics produced by a species of actinomycete under submerged fermentation conditions are useful in controlling coccidiosis in poultry and in improving feed utilization efficiency in ruminants.

Abstract: A species of Actinoplanes, designated Actinoplanes auranticolor ATCC 31011, when subjected to submerged aerobic fermentation under controlled conditions, produces a mixture of antibiotics which includes a number of macrocyclic lactones and depsipeptides. The individual compounds exhibit significant antibiotic activity. The crude antibiotic mixture or combinations of a pure macrocyclic lactone and a pure depsipeptide demonstrate marked synergistic antibiotic activity. These antibiotics act as growth promotants in chicks and swine and are effective in the treatment of swine dysentery.This mixture of antibiotics is also produced by a species of Actinoplanes designated Actinoplanes azureus ATCC 31157. In addition, this culture produces a mixture of heptaene antibiotics with antifungal properties.