Interspecies competition and inhibition within the oral microbial flora: environmental factors influence the inhibition of Streptococcus mutans by Streptococcus oligofermentans

Dental caries is a bacterial infectious disease. Streptococcus mutans is the primary pathogen that causes dental caries. Streptococcus oligofermentans is a new oral streptococcal species that can inhibit the growth of S. mutans specifically. The study aimed to assess the inhibition of S. mutans by S. oligofermentans under different oral environmental conditions. The inhibition under different carbohydrate and oxygen conditions was investigated in vitro using an interspecies interaction assay. The 4-aminoantipyine (4-ATTP) method was used to measure the yield and the initial production rate of H(2) O(2) in S. oligofermentans. The inhibitory effect was enhanced when the bacteria were cultured with carbohydrates and under aerobic conditions, or when S. oligofermentans was inoculated earlier than S. mutans. The initial synthesis rates of H(2) O(2) by S. oligofermentans were higher in the presence of carbohydrates and in aerobic culture conditions. In terms of the total H(2) O(2) yield, the effect of the environmental conditions was as follows: no carbohydrates > sucrose> glucose, and aerobic conditions > anaerobic conditions. We conclude that the presence of carbohydrate and oxygen significantly affect the ability of S. oligofermentans to inhibit the growth of S. mutans. The difference in inhibitory effect may be attributed to changes in the capacity of S. oligofermentans to produce H(2) O(2) .