Pharmaceutically active secondary metabolites of microorganisms

The antibiotics have been useful in our battles against infectious bacteria and fungi for over 50 years. However, many antibiotics are used commercial ly, or are potentially useful, in medicine for activities other than their antibiotic action. They are used as antitumor agents, immunosuppressive age nts, hypocholesterolemic agents, enzyme inhibitors, antimigraine agents, an d antiparasitic agents. A number of these products were first discovered as antibiotics which failed in their development as such, or as mycotoxins. I n addition to the above alternative applications, new powerful antibiotics have been discovered and commercialized in recent years and others are in c linical testing at the moment. A few successful secondary metabolites appea r to have no antibiotic activity. The recently increased development of res istance to older antibacterial and antifungal drugs is being met with the u se or clinical testing of older, underutilized or previously nondeveloped n arrow-spectrum antibacterial products as well as powerful semisynthetic ant ifungal agents.