Methods: Three probiotic Lactobacillus strains (L. rhamnosus GG, L. casei str. Shirota and L. reuteri SD2112) and one Bifidobacterium (B. lactis Bb12) were included in this study. The pellicles were formed on synthetic hydroxyapatite (HA) powder by first incubating clarified whole saliva, parotid saliva or buffer with the probiotic bacteria. The bacteria were then removed and supernatants incubated with HA. Control pellicles for the adherence assays were formed by coating HA first with saliva and then with the supernatant from a bacterial suspension in buffer. After pellicle formation metabolically labelled S. mutans MT8148 or S. gordonii DL1 were allowed to adhere on HA. To analyse the composition of the pellicles, proteins were released from HA with SDS, and analysed with SDS-PAGE.
Results: S. mutans and S. gordonii both adhered well to parotid saliva coated HA but only S. gordonii adhered to whole saliva coated HA. Treatment of parotid saliva with probiotic lactobacilli significantly decreased the adherence of S. mutans; this effect was also seen in control pellicles. The effect of B. lactis Bb12 was significantly lower. The adherence of S. gordonii as well as the adherence of S. mutans on whole saliva coated HA remained unaffected. Preliminary results from SDS-PAGE analysis indicate that there are differences in the protein composition of the pellicles.
Conclusion: Probiotic lactobacilli secrete or release substance/s that bind to hydroxyapatite pellicle. They may interact with proteins important for S. mutans adherence as the adherence of S. gordonii remained unaffected.
This study is supported by Turku University Central Hospital and Hilkka Brusiin foundation.