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Thiopeptin is a new antibiotic, produced by Streptomyces tateyamensisand developed solely for animal use as a feed additive. The antibiotic content in animal tissue and feed was assayed in terms of the antimicrobial activity against Mycoplasma laidlawiiA. This antibiotic was found to be relatively nontoxic in rats and mice. In chickens, this antibiotic is excreted into feces within 48 hr of administration and is not absorbed in tissue. It is well tolerated in both broilers and swine and is highly stable in animal feed. Thiopeptin-supplemented feed contributes to the improvement of weight gain, feed efficiency in chickens and swine, and the egg performance in layers. Thus, thiopeptin, when used as a feed additive, is quite suitable for supplementing animal nutrition.

The thiopeptins are a new group of sulfur-containing peptide antibiotics produced by Streptomyces tateyamensis. The antibiotic consists of a major component (designated as thiopeptin B) and four minor ones (thiopeptins A1to A4). These components were isolated by solvent extraction from mycelium followed by chromatography on silica gel with various ratios of chloroform and methanol as elution solvents. Acid hydrolysis of each of the thiopeptin components yielded 1 mole of valine, 1 of threonine, 1 of cysteine, and 2 of alanine as amino acids. Each component of the thiopeptin A group has chemical and biological properties closely similar to those of thiopeptin B, but detailed characterization has established that thiopeptins A1, A3, and A4are new antibiotics. We could not obtain accurate data for determination of the uniqueness of A2because of insufficient sample. Thiopeptin has strong antibacterial activity against gram-positive bacteria and Mycoplasma, and exhibits no cross-resistance to major human-use antibiotics.