Microbial Profile During Pericoronitis and Microbiota Shift After Treatment

Abstract

The microflora of the distal pocket is considered as the major cause of pericoronitis. How the oral microflora changes during pericoronitis and whether different types of impacted third molar harbor the same microflora are still unknown. Saliva, subgingival plaque, and gingival plaque of mandibular third molars (M3Ms) were collected from twelve patients with acute pericoronitis. They were given local irrigation or local irrigation + antibiotics according to symptoms. Samples were harvested at the first visit with pericoronitis, 1 week after treatment, and 6 weeks after treatment. 16S rRNA gene polymerase chain reaction products were generated and sequenced after DNA isolation. Comparison of three sampling sites showed that, the subgingival plaque of M3Ms had most remarkable changes in symptomatic period, including a significant increase in microbial richness, and a convergent trend in microbial composition. After treatment, the subgingival microbiome was altered and largely returned to the state in asymptomatic period. In summary, the distal subgingival microbiota of M3M was most likely to be associated with the pathogenesis of pericoronitis. The post-treatment microbiota shift of M3M proved the effectiveness of treatment. The inclination type of impacted M3Ms and treatment method would also make a difference to the pericoronal microbiota.

Keywords: 16S rRNA; microbiome; pericoronitis; sequencing; treatment.

FIGURE 1

The oral microbiota changes from asymptomatic to symptomatic period at three sampling sites: saliva, Sal; subgingival plaque, Sub; and gingival plaque, Gin (n = 12). (A) Calculation of alpha diversity values (observed species) for comparison of the total microbial diversity of saliva, subgingival plaque, and gingival plaque between asymptomatic and symptomatic periods (paired t-test, *P < 0.05, and **P < 0.01). (B) The principal coordinate analysis charts based on weighted UniFrac distance: comparisons between asymptomatic and symptomatic periods at three sampling sites. (C) A taxa heat map of the relative abundances of bacteria that differed significantly between asymptomatic and symptomatic periods at three sampling sites, respectively (Wilcoxon matched-pairs signed rank test, P < 0.05). (D) The line chart showed the amount changes (relative abundance) of bacteria that differed significantly between asymptomatic and symptomatic periods at three sampling sites (Wilcoxon matched-pairs signed rank test, *P < 0.05, and **P < 0.01).

FIGURE 2

The comparisons of microbiota between the vertically impacted (VI, n = 7) M3Ms and horizontally impacted (HI, n = 5) M3Ms in symptomatic period: subgingival plaque, Sub; gingival plaque, Gin. (A) Alpha diversity values (observed species) of subgingival and gingival plaque were analyzed between HI and VI groups (independent t-test, P < 0.05). (B) The principal coordinate analysis charts based on weighted UniFrac distance: comparisons between HI and VI groups at two sampling sites. (C) A taxa heat map of the relative abundances of bacteria that differed significantly between the HI and VI groups in subgingival and gingival plaque (Mann-Whitney U test, P < 0.05).

FIGURE 3

The subgingival microbiota changes from symptomatic to treatment period and the subgingival microbiota comparisons between asymptomatic and treatment periods (n = 12). (A) The principal coordinate analysis chart based on weighted UniFrac distance: comparison between symptomatic and treatment periods. (B) The principal coordinate analysis chart based on weighted UniFrac distance: comparison between asymptomatic and treatment periods. (C) The line chart showed the amount changes (relative abundance) of bacteria that differed significantly from symptomatic to treatment period in subgingival plaque (Wilcoxon matched-pairs signed rank test, *P < 0.05, and **P < 0.01). (D) A taxa heat map of the relative abundances of bacteria that differed significantly between symptomatic and treatment periods in subgingival plaque (Wilcoxon matched-pairs signed rank test, P < 0.05). (E) A taxa heat map of the bacterial composition of subgingival plaque in asymptomatic and treatment periods.

FIGURE 4

The comparison of microbiota changes brought by local (n = 6) and combined (n = 6) treatment: subgingival plaque, Sub; gingival plaque, Gin. (A) Alpha diversity values (observed species) were analyzed between symptomatic and treatment periods in combined treatment group (paired t-test, *P < 0.05). (B) Alpha diversity values (observed species) were analyzed between symptomatic and treatment periods in local treatment group (paired t-test, P < 0.05). (C) The principal coordinate analysis chart based on weighted UniFrac distance: comparison between local treatment and combined treatment groups. The UniFrac distance lines quantified the degree of the microbial composition variations of subgingival plaque from symptomatic to treatment period. (D) Comparison of UniFrac distance values of subgingival microflora from symptomatic to treatment period between local treatment (LT) and combined treatment (CT) groups (Mann-Whitney U test, *P < 0.05).