Periodontitis-Associated Shifts in Bloodstream Infections among Allo-HSCT Recipients

This study aimed to investigate how periodontitis would alter bloodstream infections (BSIs) in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). We hypothesized that periodontitis would alter the microbiological profile of BSIs, particularly the relative prevalence of viridans group streptococci (VGS), common oral bacteria frequently implicated in BSIs in allo-HSCT recipients, and other non-VGS organisms. We further investigated whether these microbiological changes were associated with clinical outcomes and alterations in VGS-specific humoral immune responses. A retrospective cohort ( n  = 489 patients, 2010–2020) and a prospective cohort ( n  = 149 patients, 2021–2022) were included for this observational study recruited from Princess Margaret Cancer Centre. Patients were categorized based on pretransplant history of periodontitis. BSIs occurring during the hospitalization period and mortality up to 1,000 days posttransplant were compared between patients with and without periodontitis. Pretransplant serum samples from the prospective cohort were analyzed for VGS-specific IgG and IgA using flow cytometry. There was no difference in the rates of BSI between groups; however, in the retrospective cohort, patients with a history of periodontitis had a higher incidence of non-VGS BSIs (76.7% vs. 56.8%, P  = 0.019). A similar, though nonsignificant, trend was observed in the prospective cohort (63.4% vs. 45.8%, P  = 0.16). Notably, the shift toward non-VGS BSIs was stage-dependent, increasing with advanced periodontitis in both cohorts ( P  = 0.009 and P  = 0.025, respectively). Patients with periodontitis had almost double the risk of mortality compared to those without (retrospective: hazard ratio [HR] = 1.86; 95% confidence interval [CI] = 1.31-2.69; P < 0.001; prospective: HR = 1.82; 95% CI = 0.98-3.57; P  = 0.06). Elevated VGS-specific IgG and IgA levels were observed in patients with periodontitis, with lower IgG levels correlating with VGS BSIs. History of periodontitis was associated with differences in BSI microbiology, including a higher proportion of non-VGS BSIs among patients who developed BSIs, and with poorer survival outcomes in allo-HSCT recipients.