Pyrosequencing reveals significant associations between ethnicity and the subgingival microbiome

Introduction: It is known that the composition of the subgingival microbiome is influenced by several host-associated colonization factors; however, the contributions of ethnicity to bacterial colonization have been little explored. Since it is known that periodontal diseases have a racial and ethnic predilection, it is important to examine the effect of ethnicity on bacterial colonization in health. Objective: To compare the subgingival microbial profiles of periodontally healthy subjects belonging to four different ethnicities using next generation sequencing for bacterial identification and characterization. Methods: 100 periodontally healthy subjects of Caucasian (n=25), African-American (n=25), Hispanic (n=25), and Chinese (n=25) ethnicities were recruited. All subjects were adults without history of systemic disease, pregnancy, and recent or prophylactic antibiotic use. Subgingival plaque samples were collected, DNA isolated, and massively-parallel titanium bacterial tag-encoded FLX amplicon pyrosequencing was performed. Chimera-depleted sequences were compared against a locally-hosted curated database for bacterial identification. Shannon Diversity index and total number of species were computed. Non-parametric tests were used to compare bacterial levels between ethnic groups. Results: No differences were observed in the total number of species between ethnic groups. African Americans demonstrated significantly lower bacterial diversity than the other three ethnicities. African-American's biofilms contained significantly more Streptococcus and less Prevotella genera than the other three ethnicities. The genera Treponema and Porphyromonas were detected in fewer African-Americans and Caucasians than Hispanics and Chinese. The genus Neisseria was signifcanly more prevalent in Chinese than the other three ethnicities. Conclusions: There is a significant association between ethnic preference and the bacterial composition of the health- compatible subgingival biofilm. However, the relative contributions of genetics and shared environment remain to be investigated. This research was supported by the Ohio State College of Dentistry CTOC T32 DE 0143220 training grant.