Storage of Specimens at 4¡C or Addition of Sodium Fluoride (1%) Prevents Formation of Ethanol in Urine Inoculated with Candida albicans

Published: Journal of Analytical Toxicology, Volume 23, Number 5, September 1999, pp.333-336 .

Storage of Specimens at 4°C or Addition of Sodium Fluoride (1%) Prevents Formation of Ethanol in Urine Inoculated with Candida albicans

A.W. Jones, L. Hylén, E. Svensson, and A. Helander

The microbial synthesis of ethanol was investigated in urine specimens containing 0.5% or 1.0% (w/v) glucose and inoculated with the yeast Candida albicans (100 cfu/mL). Aliquots (10 mL) of urine were dispensed into plastic tubes containing enough sodium fluoride to give final concentrations of 0.1%, 0.25%, 0.5%, 0.75%, 1%, and 2% (w/v), and C. albicans was added. The tubes were tightly stoppered and allowed to stand either at room temperature (22°C) or in a refrigerator (4°C) for up to 34 days before concentrations of ethanol were determined by headspace gas chromatography. Urine samples stored at 22°C without sodium fluoride produced 0.25 g/L ethanol after two days, and the concentration increased to 2.10 g/L and 4.50 g/L after eight days for specimens containing 0.5% (w/v) and 1% (w/v) glucose, respectively. The ratio of the serotonin metabolites 5-hydroxytryptophol/5-hydroxyindoleacetic acid (5HTOL/5HIAA) in urine remained within the reference range (< 15 pmol/nmol) despite high concentrations of ethanol being produced. Urine samples kept at 4°C did not produce any ethanol (< 0.01 g/L) even without sodium fluoride present as a preservative. The production of ethanol by C. albicans was stopped completely by adding 1% or 2% (w/v) sodium fluoride but not by concentrations of 0.75% (w/v) or less. The microbial synthesis of ethanol in urine samples initially stored at room temperature without sodium fluoride was slowed down considerably by moving them into a refrigerator at 4°C. In conclusion, the production of ethanol in urine by C. albicans can be prevented by storage of samples in a refrigerator at 4°C or by adding sodium fluoride ³ 1% (w/v). Measuring the ratio of 5HTOL/5HIAA can help to distinguish postsampling production of ethanol from metabolism and excretion processes.

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