October 23, 2014

COLUMBUS, Ohio, USA: Microbiologists have suggested that bacteria present in the oral cavity are a reliable indicator of a person’s ethnicity. In a study of participants from four different ethnic groups, they found that each group had an individual set of oral microbes. They believe that these microbes might also predispose individuals to certain oral diseases. The study included 192 healthy individuals aged 18 and over who consisted of non-Hispanic blacks, non-Hispanic whites, Chinese people and Latinos. Researchers at the Ohio State University compared the oral microbial communities they obtained from bacterial samples from the participants’ saliva, tooth surfaces and gums after sequencing their DNA. Using a special machine, they were able to predict an individual’s ethnicity with 62 percent accuracy based on a given bacterial community. African-Americans were correctly identified according to their microbial signature 100 percent of the time. Latinos were identified with 67 percent accuracy and Caucasians with 50 percent. The classifying machine performed best when subgingival microbes were used. This was attributed to the fact that these bacteria are the least likely to be disrupted by environmental changes in the mouth, such as food, toothpaste and tobacco. Overall, they found 398 species, with an average of about 150 species per person. Only 2 percent were present in all study participants in different concentrations according to their ethnicity. According to the scientists, the findings could help explain why some ethnic groups, and African-Americans in particular, are more susceptible to gum disease and provide further evidence of the necessity of personalized dental treatments. The study, titled “Deep Sequencing Identifies Ethnicity-Specific Bacterial Signatures in the Oral Microbiome,” was published online on Oct. 23 in the PLOS ONE journal.

www.dental-tribune.com

October 23, 2014

AUSTIN, Texas, USA: Studies on the human microbiome have shown that shifts in oral microbiota are associated with a number of diseases, including obesity, Crohn’s disease, diabetes and periodontitis. Now, U.S. scientists have found that oral bacteria act differently in diseased patients compared with healthy individuals. They believe that the findings could be used to develop methods to prevent or even reverse diseases such as periodontal disease. Although it is known that the composition of the microbiome changes during the transition from health to disease, it is still unclear how specific activities of different members of the microbial community affect diseases. In order to understand how different bacteria act in healthy and diseased individuals, researchers at the University of Texas at Austin examined periodontal plaque samples from ten patients from Izmir in Turkey with aggressive periodontitis. Using supercomputers, the researchers compared the expression of 160,000 genes in healthy and diseased periodontal communities and found that these communities show defined differences in metabolism. “In other words, a species of bacteria that ate one thing, such as fructose, can switch to a different kind of sugar to feed on if diseased,” explained Dr. Marvin Whiteley, professor of molecular biosciences at the university. A major question concerning the mechanism underlying the changes is whether changes in composition and behavior cause diseases or are a consequence of diseases. In this respect, the present study demonstrated that differential expression of metabolic genes was associated with the periodontal disease state. For instance, the expression of butyrate production genes by the bacterium Fusobacterium nucleatum increased during disease, suggesting that F. nucleatum butyrate production promotes periodontitis. However, further studies are needed to verify this hypothesis, the researchers said. Whiteley said that the research could help determine biomarkers that predict whether a patient is at risk of developing periodontitis. As bacterial populations can be manipulated, researchers might be able to shift them back to that of a healthy microbiome . The findings may thus also benefit periodontal treatment. According to the latest figures provided by the Centers for Disease Control and Prevention, about 47 percent of adults aged 30 and over in the U.S. have periodontitis. The organization estimates that over 8 percent of adults have severe periodontitis. The study, titled “Metatranscriptomics of the Human Oral Microbiome during Health and Disease,” was published in the April issue of mBio, an open-access journal published by the American Society for Microbiology.

www.dental-tribune.com