Abstract:

Considering that lactic acid bacteria (LAB) that can inhibit harmful bacteria, LAB strains stored in our laboratory
were screened for inhibiting oral Streptococcus mutans. The screened strains were measured for minimum inhibitory
concentration (MIC) and inhibitory effect on biofilm formation adhesion properties of S. mutans, and the underlying
mechanism was preliminarily studied as well. The results showed that 5 Lactobacillus plantarum strains including K25,
SKT109, YW3-2, YW5-1 and YW1-1 exhibited clear inhibition against S. mutans. Among 4 indicator S. mutans strains,
1.2499 and 1.2500 were more sensitive to L. plantarum. L. plantarum K25 showed stronger inhibition than 4 other strains
against S. mutans. The MIC value (1.25 × 107–2.50 × 107 CFU/mL) of strain K25 was the lowest, the inhibition rate on
biofilm formation of S. mutans was significantly higher, and the inhibitory effect on the adhesion ability of S. mutans was
clear. Preliminary studies on the antibacterial mechanism of L. plantarum K25 indicated that lactic acid and hydrogen
peroxide produced by the strain played major roles in this activity.

Key words: Streptococcus mutans, probiotic, Lactobacillus plantarum, inhibitory activity