Acid production and growth by oral Lactobacillus species in vitro

AIM: To analyze the acid-producing and growth abilities of different oral Lactobacillus species. METHODS: Thirty-nine oral clinical strains and type strains of Lactobacillus, representing nine species, including Lactobacillus casei/paracasei, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus mucosae, Lactobacillus oris, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus salivarius, and Lactobacillus vaginalis were studied. Anaerobically-grown bacterial cells were inoculated overnight in de Man, Rogosa, and Sharpe broth containing 2% glucose (pH 7.0). Acid production and growth were measured at 0, 1.5, 3, 5, 7, and 24 h. RESULTS: Lactobacillus salivarius, Lactobacillus rhamnosus, Lactobacillus casei/paracasei, and Lactobacillus plantarum grew rapidly and reached an optical density higher than other species. They also produced more acid than the others. Lactobacillus vaginalis showed the lowest rate of growth and acid production. These findings demonstrated that the different species of Lactobacillus showed different abilities to generate acid, allowing the species to be categorized into three groups: strongly, moderately, and weakly acidogenic. CONCLUSION: There was variation in acid production and growth between the Lactobacillus species. The strongest acid producers were Lactobacillus salivarius, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus casei/paracasei, respectively. It seems possible that these species might play a more important role in caries development than the others.