Structure-activity studies among 16-membered macrolide antibiotics related to tylosin

Although a substantial number of 16-membered macrolides related to tylosin have now been isolated and evaluated as antibiotics, none appeared to be superior to tylosin in treating bacterial or mycoplasmal infections caused by sensitive organisms. Nevertheless, this comparison of the antibiotic activity of 16-membered macrolides clearly indicates that novel antibiotics with potentially useful activity can be obtained from mutant strains which have been blocked at various steps in their biosynthesis of antimicrobial agents. The novel compounds thus produced may also be used as starting materials for additional chemical and microbiological modification. Furthermore, the mutant strains which produced these novel compounds should be useful recipients for interspecific genetic recombination by protoplast fusion or gene cloning to yield hybrid antibiotics. Even greater exploitation of these methods will be required in the continuing search for new antibiotics and improved methods for producing them.