New findings in actinomycosis described from Tohoku University, Division of Pediatric Dentistry
2009 JUL 21 - (NewsRx.com) -- New investigation results, 'Transient acid-impairment of growth ability of oral Streptococcus, Actinomyces, and Lactobacillus: a possible ecological determinant in dental plaque,' are detailed in a study published in Oral Microbiology and Immunology. "Dental plaque pH decreases to about 4 through bacterial fermentation of carbohydrates and this low pH is maintained for from several minutes to about an hour. Repeated acidification causes demineralization of the tooth surface, resulting in caries formation," investigators in Sendai, Japan report. "The acidification also influences plaque bacteria. Severe acidification kills bacteria efficiently, while physiological acidification, the condition occurring in plaque, kills bacteria partially and may impair growth ability. We, therefore, investigated the effects of physiological acidification on representative caries-related bacteria. Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis, Streptococcus oralis, Lactobacillus paracasei, and Actinomyces naeslundii were used. Effects of physiological acidification at pH 4.0 on cell viability and growth ability, as well as the growth rate of these bacteria at pH 4.0-7.0, were investigated. Mutans streptococci and Lactobacillus grew at pH 4.0 but the growth of S. sanguinis and S. oralis ceased below pH 4.2 and pH 4.2-4.4, respectively. Acidification at pH 4.0 for 1 h killed 43-89%, 45% and 35-76% of S. sanguinis, S. oralis, and Actinomyces, respectively. Furthermore, assessment of bacterial growth curves revealed that the growth ability of the surviving cells of S. sanguinis, S. oralis and Actinomyces was impaired, but it was recovered within 2-5 h after the environmental pH had returned to 7.0. The acidification neither killed nor impaired the growth of mutans streptococci and Lactobacillus," wrote M. Horiuchi and colleagues, Tohoku University, Division of Pediatric Dentistry. The researchers concluded: "These results indicate that physiological and transient acidification is not sufficient to kill bacteria, but it causes a temporary acid-impairment of their growth ability, which may function as an ecological determinant for microbial composition in dental plaque." Horiuchi and colleagues published their study in Oral Microbiology and Immunology (Transient acid-impairment of growth ability of oral Streptococcus, Actinomyces, and Lactobacillus: a possible ecological determinant in dental plaque. Oral Microbiology and Immunology, 2009;24(4):319-24). For additional information, contact M. Horiuchi, Tohoku University Graduate School of Dentistry, Division of Pediatric Dentistry, Sendai 980-8575, Japan. The publisher of the journal Oral Microbiology and Immunology can be contacted at: Blackwell Publishing Inc., 350 Main St., Malden, MA 02148, USA. Keywords: Japan, Sendai, Actinomycosis, Dental Plaque, Dentistry, Immunology, Pediatric, Physiology. This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2009, Life Science Weekly via NewsRx.com.
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