[Comparison of subgingival microbial profile of aggressive periodontitis, chronic periodontitis and periodontally healthy individuals].

Objective: To compare the subgingival microbiota of subjects from patients with aggressive periodontitis (AgP), chronic periodontitis (CP) and periodontally healthy (PH) individuals, respectively. Methods: Volunteers were recruited from the Nangjing Stomatological Hospital, Medical School of Nanjing University during December 2013 to December 2014. Ten individuals were included in each of three groups. Preliminary estimation of sampling sites was chosen based on the X-ray and intraoral examination. Then the subgingival plaque samples were collected, the periodontal clinical indices were recorded, genes were extracted and amplified by PCR, and subsequently a DNA library was constructed for 16S rDNA sequencing. The library that can be successfully constructed and sequenced includes: 18 samples from 8 AgP group patients, 31 samples from 10 CP group patients and 10 samples from 8 PH group volunteers. Finally, we analyzed and compared the α-diversity, β-diversity and microbial compositions of samples in each group. Pearson correlation analysis was adopted to evaluate the correlation between the relative abundance of microorganisms and the probing depth (PD). Results: The α-diversity of subgingival flora in AgP group was significantly lower than that in PH group and CP group, respectively (P<0.05). On the phylum level, the abundance of Bacteroides [(36.8±7.4)%] and Spirochetes [(16.0±5.4)%] in AgP group and the abundance of Bacteroides [(37.2±6.3)%] and Spirochetes [(11.8±3.6)%] in CP group were significantly higher than those in PH group [(27.5±11.2)%, (5.2±4.4)%, respectively, P<0.05]. While the relative abundance of Actinomycetes and Proteobacteria [(4.2±3.3)%, (12.9±5.1)%, respectively] in AgP group and that of CP group [(6.1±2.6)%, (12.1±4.0)%, respectively] were significantly higher than PH group [(19.3±13.1)%, (23.0±10.1)%, respectively, P<0.01). The abundance of Spirochetes and Tenericutes in AgP group [(16.0±5.4)%, (1.7±1.2)%, respectively] were significantly higher than that in CP group [(11.8±3.6)%, (0.7±0.6)%, respectively, P<0.05]. At the genus level, Corynebacterium, Actinomycete, Saccharibacteria_norank, Selenomonas and Oribacterium in the subgingival flora of AgP group were significantly lower than that of CP group, while the relative abundance of Actinomycetes, Lentimicrobiaceae_norank, Defluvitaleaceae_UCG_011, Family_XI_unclassified were significantly higher than that of CP group (P<0.05). Principal coordinate analysis showed that samples of each group clustered separately from each other. Linear discriminant analysis revealed that the bacteria enriched in AgP group included Spirochetes, while in CP group included Bacteroidaceae. The result of correlation analysis showed that the abundance of the following genera in AgP group were positively correlated with PD: Treponema_2, Defluitaleaceaeae_UCG_011, Mycoplasma, Catonella, Fretibacterium (r=0.525-0.750, P<0.05). While the relative abundance of Comamonadaceae_unclassified, Streptococcus, Capnocytophaga, Neisseria, Prevotella, Peptococcus, Ralstonia, Bergenia and Actinomycetes were negatively associated with PD (r=-0.617--0.490, P<0.05). In the CP group, the abundance of Dialister, Family_XI_unclassified, Catonella, Peptococcus, Pelospora and Rikenella_RC9_gut group were positively correlated with PD (r=0.430-0.533, P<0.05). Conclusions: There is a clear difference between the subgingival flora of periodontal patients and that of PH individuals. Besides, subgingival flora of AgP and CP are also different, suggesting that these could be two different diseases.