Antibacterial activity of probiotic candidates for oral health.

The aim of this study was to determine the probiotic potential of autochthonous oral lactobacilli. For this, 66 strains were screened for antibacterial activity against two cariogenic strains (Streptococcus mutans and Actinomyces viscosus) and two periodontopathogenic strains (Fusobacterium nucleatum and Porphyromonas gingivalis). The inhibitory activity was investigated with the agar overlay technique. Positive results led us to explore some mechanisms of action. The ability to produce H(2)O(2) and the glycerol dehydratase gene were searched among all the strains. The gassericin A gene was checked among the Lactobacillus gasseri. All the tested strains inhibited S. mutans and A. viscosus; only one did not inhibited F. nucleatum and 52 strains inhibited slightly the growth of P. gingivalis. No inactivation of antibacterial activity was observed after treatment with proteinase K. The gene of the gassericin A was not found in any strain. Only one strain showed a 275-bp amplicon corresponding to the Glycerol Dehydratase gene. This strain has been identified by DNA 16S sequencing as a L. gasseri. Among the 66 tested strains, 7 produced hydrogen peroxide. Our findings suggest that in addition to the previous results, some of the autochthonous oral lactobacilli tested could be considered as suitable probiotics.