Acid-producing capacity from sugars and sugar alcohols among Lactobacillus isolates collected in connection with radiation therapy.

OBJECTIVE: To investigate the acid-producing capacity from sugars and sugar alcohols of oral Lactobacillus collected in connection with radiation therapy (RT) to the head and neck region.

DESIGN: Lactobacillus were collected from the tongue, buccal mucosa and supragingival plaque in 24 patients before, during, and after RT. The acid-producing capacity of Lactobacillus isolates (n=211) was analyzed using a colorimetric fermentation test in microtiter plates. Solutions containing 2% sugars (sucrose, glucose, fructose, lactose) or sugar-alcohols (sorbitol and xylitol) were used. After 24h of incubation, bacterial acid-producing capacity was determined as strong (pH<5), weak (pH  ≥5-≤ 6) or low/absent (pH>6). Data regarding intake frequency of sugar-rich products and products with sugar-alcohols was collected.

RESULTS: The highest acid-producing capacity using the sugars was seen for isolates collected during RT. Sorbitol was fermented to a higher extent during and post RT, especially among isolates from plaque. Lactobacillus fermenting xylitol showed the highest acid-producing capacity during RT (p<0.05). No statistically significant correlations between stimulated whole salivary secretion rate and acid-producing capacity, or between the intake frequency of sugar-rich products or sugar-alcohol containing products and Lactobacillus acid-producing capacity, were found.

CONCLUSION: The results suggest that Lactobacillus isolates, collected from the tongue, buccal mucosa and supragingival plaque, have a higher acid-producing capacity using sugars and sugar-alcohols during RT than one year post RT.