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

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). ...

Rapid microbiological assay of serum vitamin B 12 by electronic counter.

A new method of measuring the growth of Lactobacillus leichmannii is reported. Its adoption for the estimation of serum vitamin B(12) levels shortens the incubation period required to five hours at 45 degrees C. The method is compared statistically with a standard method of estimation, requiring incubation at 37 degrees C., by duplicate determinations on 106 hospital patients. The significance ...

Microbiological assay for vitamin B12 performed in 96-well microtitre plates.

A simplified microbiological assay for vitamin B12 estimation, completed on microtitre plates using a colistin sulphate resistant strain of Lactobacillus leichmannii (NCIB 12519), and cryopreserved cultures is described. The new assay correlated well with a more conventional "tube" assay and was not influenced by the presence of antibiotics in serum. Evaluation of assay performance showed excel...

The microbiological assay of vitamin B12 with Lactobacillus leichmannii.

Liquid Nitrogen Freezing in Microbiological Assay Systems. I. Preservation of Lactobacillus Leichmannii for Direct Use in the Vitamin B12 Assay.

Suspensions of Lactobacillus leichmannii were stored in liquid nitrogen and were used as direct inocula in vitamin B(12) assays. Complete recovery of viable cells was obtained when the suspensions in basal B(12) medium were rapidly frozen by direct immersion into liquid nitrogen and rapidly thawed by agitating the suspensions in a water bath at 40 C. Greater than 90% destruction occurred when t...