Lactobacillus species in supragingival plaque in subjects with hyposalivation

Abstract

The aim was to analyse frequency and proportion of Lactobacillus species in supragingival plaque in subjects with hyposalivation and the Lactobacillus species ability to ferment sucrose, mannitol, sorbitol and xylitol.Material and methods: Ten subjects treated with radiation therapy (RT), 10 subjects with primary Sjögren's syndrome (pSS), and matched controls were included. Supragingival plaque was collected interproximally 12–13 and 15–16 and analysed using cultivation technique. Lactobacillus colonies were randomly selected and stored at −70°C. The Lactobacillus strains fermentation pattern was analysed using basal medium with 1% of respective carbohydrate/sugar alcohol added.Results: Lactobacilli were more frequent at site 15–16 than at site 12–13. Lactobacilli were about twice as frequent in the pSS and RT groups than in their respective control group. For those harbouring lactobacilli, the proportion of the total count at site 15–16 was 13 ± 27% for the RT group and 0.003 ± 0.003% for their controls, 3.2 ± 5.8% for the pSS group and 0.06 ± 0.2% for their controls. We have further analysed 28 of 114 collected Lactobacillus strains. All strains gave a pH <6.0 and at 95% a pH <5.5 at sucrose fermentation. Mannitol could be fermented by 82% of the strains, sorbitol by 75% and xylitol by 64%. A pH <5.5 was obtained for 82% of the strains with mannitol, 75% with sorbitol and 32% with xylitol.Conclusion: Subjects with hyposalivation have a marked increase in lactobacilli. Of the strains analysed this far 95% gave a pH <5.5 at sucrose‐fermentation. A pH <5.5 was obtained for 82% of the strains with mannitol, 75% with sorbitol and 32% with xylitol. As those sugar substitutes are included in tooth pastes, chewing gums and saliva‐stimulating tablets and sprays, it is likely that the lactobacilli are further promoted in subjects with hyposalivation.