ISP Medium 1 Difco 276910, 500g. International Streptomyces Project - Tryptone Yeast Extract Broth. Used for characterizing Streptomyces species according to the International Streptomyces Project (ISP). ISP Medium 1 Difco 276910 - buy online through Voigt Global Distribution, your dealer distributor for all BBL DIFCO BD Microbiology products.