B12 Culture Agar USP Difco 254110, 100g. To maintain cultures of Lactobacillus delbrueckii and for use in USP and AOAC methods for microbiological assay of Vitamin B12. B12 Culture Agar USP Difco 254110 - buy online through Voigt Global Distribution, your dealer distributor for all BBL DIFCO BD Microbiology products.