Bacterial-host interactions in periodontal prognosis: Role of P. gingivalis and IL-8

The combined effects of Porphromonas gingivalis with other pathogens and host inflammatory on treatment prognosis remain underexplored. This study investigated associations between P. gingivalis bacterial co-infection, salivary IL-8 levels, and prognosis following non-surgical periodontal therapy (NSPT).

Seventy-four participants underwent NSPT were recruited. Subgingival specimens were collected before treatment and analyzed by 16S rRNA sequencing. Salivary IL-8 levels and periodontal clinical parameters were recorded at baseline and one month after scaling and root-planing (SRP). Saliva samples were analyzed for IL-8 levels using a commercial kit. Multivariate regression analyses were conducted to assess associations between pathogens, IL-8, and prognosis.

Participants with Prevotella intermedia had significantly higher IL-8 levels at baseline and post-treatment (P = 0.03 and P < 0.01). P. gingivalis was associated with significantly higher percentages of sites with PD ≥ 5 mm at both time points (P = 0.04 and P = 0.02). After adjusting for IL-8 and smoking, P. gingivalis was associated with higher residual PD ≥ 5 mm (5.11 %, P < 0.05), but lost significance after adjusting for oral health behaviors. After full adjustment, baseline P. gingivalis without Aggregatibacter actinomycetemcomitans was associated with higher residual PD ≥ 5 mm (7.83 %, P < 0.05), whereas co-infection attenuated this association (-0.49 %, P > 0.05).

P. gingivalis was associated with residual PD ≥ 5 mm, with its effect modified by smoking status, IL-8 levels, and oral health behaviors. Although co-infection with A. actinomycetemcomitans showed no significant effect, the attenuating trend warrants further investigation.