The influence of penicillin on Lactobacillus leichmannii serum B12 assay

The influence of penicillin on Lactobacillus leichmannii serum B(12) assay.

The influence of penicillin on vitamin B(12) assay using L. leichmannii as the test organism was investigated, and it was found that penicillin even in a low serum concentration invalidated the test.

The microbiological assay of vitamin B12 with Lactobacillus leichmannii.

Extraction of serum vitamin B12 for radio-isotopic and Lactobacillus leichmannii assay.

The protein precipitates discarded during the extraction process of the Lactobacillus leichmannii vitamin B12 assay have been shown to contain significant amounts of vitamin B12. This loss of vitamin B12 provide a satisfactory explanation for many of the descrepancies between the serum vitamin B12 values obtained by the L. leichmannii method and the radio-isotopic method of Raven et al (1969). ...

The use of potassium cyanide in the lactobacillus leichmannii assay for vitamin B12.

Studies by several investigators (Stokstad, Dornbush, Franklin, Hoffmann, Hutchings, and Jukes, 1949; Skeggs, Nepple, Valentik, Huff, and Wright, 1950) have indicated that an increased growth response was obtained to liver concentrates with thioglycolic or thiomalic acids when vitamin B12 activity was determined with Lactobacillus leichmannii. This was attributed to the prevention, by such redu...

Survival of Lactobacillus Leichmannii in Relation to Vitamin B12 Assays.

Since washed cells of Lactobacillus leichmannii ATCC 7830 frequently showed erratic results in vitamin B(12) assays, a depletion technique was used to stabilize the inoculum. The method consisted of incubating the twice-washed cells at 37 C for 45 min in distilled water. Survival and growth studies indicated that the stabilizing procedure (i) did not affect cell numbers, (ii) was optimal for de...