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Effect of antimicrobial agents on the Euglena method of serum vitamin B12 assay
  1. J. T. Lie2,
  2. Berta Ungar,
  3. D. C. Cowling
  1. Department of Clinical Pathology, Royal Melbourne Hospital, Victoria, Australia


    Antimicrobial agents in the serum may affect the results of the Euglena method of serum vitamin B12 assay. Sulphonamides suppress the growth of Euglena in concentrations attainable in the serum during treatment; streptomycin, chlortetracycline, erythromycin, kanamycin, and nitrofurantoin bleach Euglena but only when present in concentrations far exceeding the normal peak therapeutic blood levels. False low results of serum vitamin B12 assay due to inhibitory and/or bleaching substances in the serum can be readily detected by microscopy of the assay cultures and Euglena cell counts.

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    • 2 Size of Euglena inoculum (day 0): 0·2 × 105 cells/ml.

    • 1 Data from Goodman and Gilman (1965) and Carroll, Brennan, and Jacques (1955); the assay serum was diluted 1 in 80.