K-053. Selenium Availability Influences the Antimicrobial Action of Stannous Salts against Treponema denticola

S. Jackson-Rosario, R. Tarrien, C. Korsvik, W. T. Self;
Univ. of Central Florida, Orlando, FL.

Background - Many studies have indicated that oral spirochetes are associated with periodontal disease. Although few of these organisms have been characterized, the best studied is Treponema denticola. This pathogen produces proteolytic enzymes and ferments amino acids through Stickland reactions for energy metabolism. The central enzyme involved in Stickland fermentation is glycine reductase, a selenoenzyme. As such, T. denticola requires selenium for growth. Stannous salts inhibit growth of T. denticola. The mechanism of this inhibition is not understood. Previous studies have demonstrated an inverse relationship between the concentrations of selenium and tin in biological systems. In this study we examine the impact of selenium supplementation on the antimicrobial action of stannous salts in T. denticola. Methods - T. denticola was cultivated in 1375 NOS Spirochete medium (ATCC) under anaerobic conditions enriched with 4-10% CO2 at 37ºC. Varying amounts of sodium fluoride, stannous fluoride and stannous chloride were added to cultures. Cultures were supplemented with either sodium selenite or L-selenocysteine and incubated for 48 hours. Growth was monitored by measuring optical density at 600 nm. Radioisotope selenium (75Se) incorporation was followed to determine selenoprotein synthesis. Total protein synthesis was followed by incorporation of 35S-labeled methionine/cysteine. Results - We have found that addition of selenium in the form of selenite or L-selenocystine to the growth media significantly reduces the inhibitory action of stannous fluoride and stannous chloride on growth of T. denticola. However, selenium supplementation does not impact the inhibitory activity of sodium fluoride. Conclusion -T. denticola depends on selenium for growth. The results obtained in this study indicate that the antimicrobial activity of stannous salts is affected by the addition of selenium to the culture medium. These results suggest that stannous salts may target selenium metabolism in this organism and that other agents that inhibit selenoprotein synthesis could be novel antimicrobials that enhance oral health.