A comparison of seven strains of Lactobacillus casei var. rhamnosus in relation to their use in the microbiological assay of serum folate

Effect of Tween 80 on incubation period of Lactobacillus casei assay of serum folate

Contamination of folic acid assay medium with oleate led to a lag phase when Lactobacillus casei cultures were grown on folic acid but not when whole serum provided the folate source. This led to high assay values when using 20-hour incubation periods but satisfactory results were obtained after 48 hours' incubation. The addition of Tween 80 to the medium eliminated the lag phase and the assay results were consistent after 13, 24, and 48 hours' incubation.

Continuous-flow automation of the Lactobacillus casei serum folate assay

A method is described for the continuous-flow automation of the serum folate assay using Lactobacillus casei. The total incubation period is approximately four hours. The growth response of the organism to folate is estimated by measuring the rate of reduction of 2,3,5-triphenyl tetrazolium chloride (TTC). A simple continuous culture apparatus is used to grow the inoculum. Supplementation of the assay medium is necessary to obtain parallel results. A statistical assessment shows a favourable comparison with the whole-serum tube assay using a chloramphenicol resistant strain of L. casei. The method is less sensitive to inhibitory substances than the tube assay.

Acute folate deficiency in surgical patients on aminoacid/ethanol intravenous nutrition

Acute folate deficiency with pancytopenia and megaloblastic haemopoiesis developed in four patients after abdominal operations; all four responded to folic acid over 3-9 days. Three of them had been given intravenous nutrition with amino-acid/ethanol before the blood changes developed. A prospective study of twenty-five surgical patients with gastrointestinal diseases revealed a high frequency of acutely developing negative folate balance. Megaloblastic haemopoiesis and consequent blood changes were found in five patients. Treatment with intravenous nutrition correlated strongly with a fall in serum-folate and megaloblastic haemopoiesis. Some surgical patients develop acute folate deficiency which may proceed to megaloblastic arrest of haemopoiesis. Patients receiving intravenous nutrition containing ethanol are especially prone to this complication, which may be life-threatening if untreated. It is not yet known whether other forms of intravenous nutrition carry a similar risk.