Tinsdale Enrichment BD Difco™ 6 x 15 ml. BD Difco™ Tinsdale Enrichment Desiccated is used with BD Difco™ Tinsdale Agar Base(Cat. No. 278610) for primary isolation and differentiation of Corynebacterium diphtheriae.The enrichment contains bovine serum and horse serum which provide essential growth factors.L-cystine and sodium thiosulfate provide sulfur for H2S production. Potassium tellurite is a selectiveagent. The formation of black to brown halos surrounding the colony results from the reduction of potassium tellurite by H2S to metallic tellurite. Stabbing the complete Tinsdale Agar with an inoculating needle accentuates darkening of the medium by C. diphtheriae. Use with: Tinsdale Agar Base (Cat. No. 278610).