Subgingival bacterial clusters and serum antibody response as markers of extent and severity of periodontitis in adult Chinese

This study evaluated the associations between clinical, microbiological, and antibody activity manifestations of periodontitis in 123 adult rural Chinese subjects with no dental intervention. All participants were registered for full‐mouth clinical attachment level (CAL) and pocket probing depth (PD) measurements, and microbial samples were taken from four sites and analyzed for 18 different bacterial species using the ‘checkerboard’. Serum from each individual was analyzed to determine the antibody activity against the same 18 species. Exploratory factor analysis disclosed two microbial factors – Factor 1, consisting of seven species associated with periodontal health (‘early colonizers’); and Factor 2, consisting of eight species associated with periodontitis (‘putative periodontopathogens’) – which explained 87% of the variation among the microbial variables. Factor 2 was consistently associated with disease‐severity measures, whereas the ‘early colonizer’ factor was not. The antibody response showed weak or no correlations with bacterial load or with disease severity. We conclude that the bacteria investigated are resident in the subgingival plaque; that their load and proportions in the pocket may be ecologically driven; and that the antibody response is based on bacterial carrier state rather than on disease. The different antibody‐response pattern found between the individuals may suggest that each individual could be classified as a good or a weak immune responder.