Tonsillolith: not just a stone but a living biofilm

To study the morphology and activity of tonsilloliths, demonstrating oxygen respiration, denitrification, and acidification on exposure to sucrose.

Tonsilloliths were extracted in atraumatic conditions during tonsillectomy from 16 adults and sent to two different laboratories for histological, bacteriological, and biofilm studies under sterile conditions.

Multicenter laboratory study.

Multiple tonsilloliths from two patients examined by confocal microscopy and microelectrodes were used to measure aerobic/anaerobic respiration and acid production (dissolved oxygen, nitrous oxide, pH) when exposed to saliva following addition of sucrose and fluoride.

Morphologically, tonsilloliths were similar to dental biofilms, containing corncob structures, filaments, and cocci. Microelectrodes showed that the microorganisms respired oxygen and nitrate. The oxygen concentration in the center of the tonsillolith was depleted to approximately one-tenth of that of the overlying fluid. The addition of sucrose resulted in acid production within the tonsillolith, dropping the pH from 7.3 to 5.8. The data showed stratification with oxygen respiration at the outer layer of tonsillolith, denitrification toward the middle, and acidification toward the bottom. The depletion of oxygen and acid production following addition of sucrose may allow the proliferation of anaerobic/acidophilic bacteria. Fluoride suppressed acid production in the presence of sucrose.

Tonsilloliths exhibit biofilm structure and the formation of chemical gradients through physiological activity. Although tonsillectomy is an option for treating cryptic infections, understanding the morphology and biofilm characteristics of tonsilloliths may stimulate scientists to use limited or targeted remedies in the future.