Cariogenicity of the probiotic bacterium Lactobacillus salivarius in rats

Probiotic bacteria such as lactobacilli and bifidobacteria are considered to be non-pathogenic and non-toxigenic on the basis of long years of safe usage. However, some species of lactobacilli are thought to be associated with the development of dental caries. The purpose of the present study was to examine the cariogenicity of the probiotic bacterium Lactobacillus salivarius in rats. Rats were divided into six groups, and infected with L. salivarius LS1952R and/or Streptococcus mutans MT8148R. L. salivarius LS1952R became established in the oral cavity of rats and induced significant level of dental caries even when infected for only 5 days from 18 to 22 days of age. In addition, the caries scores of rats superinfected with both Streptococcus mutans MT8148R and L. salivarius LS1952R from 18 days of age were significantly higher than those infected with either L. salivarius LS1952R or S. mutans MT8148R alone. Since strain LS1952R can adhere to saliva-coated hydroxyapatites, it is concluded that L. salivarius strain LS1952R possesses an inherent cariogenic activity following adherence to the tooth surface.