Ex vivo decontamination of yeast-colonized dentures by iodine-thiocyanate complexes

Under well-defined experimental conditions, and in the presence of hydrogen peroxide, lactoperoxidase produces stable iodine-thiocyanate complexes that have antimicrobial properties. A novel process was developed to short circuit the consumption of hydrogen peroxide by microbial catalases by producing iodine-thiocyanate complexes prior to contact with microorganisms, with the aim of being able to decontaminate the ex vivo dentures colonized by yeasts.

Teabags containing lactoperoxidase adsorbed on inert clay beads were immersed for 1 minute in phosphate buffer solution (0.1 M pH 7.4) containing 5.2 mM potassium iodide, 1.2 mM potassium thiocyanate, and 5.5 mM hydrogen peroxide. After removing the adsorbed lactoperoxidase, the stability and efficacy of iodine-thiocyanate complexes for Candida-colonized denture decontamination were verified. Investigations were performed in vitro on Candida albicans ATCC 10231 and on clinical isolates from 46 dentures. A Candida plate count was performed after a 24-hour incubation at 37°C on Sabouraud-chloramphenicol or CHROMagar solid media; then, the yeast growth was evaluated in Sabouraud broth by turbidimetry and biofilm biomass by crystal violet staining.

In vitro tests demonstrated the effectiveness of the oxidant solution in sterilizing a suspension of 10⁶Candida cells per milliliter after a 5-minute incubation. A single ex vivo immersion of contaminated dentures in a solution of iodine-thiocyanate complexes led to a decrease of at least 1 log unit in the number of colony-forming units in 58.3% of the tested dentures, while immersing in water alone had no effect on denture colonization (significant c2: p = 0.0006).

These data suggest a promising new strategy for decontamination of dentures.