Infective endocarditis and post-treatment bacteremia caused by oral microorganisms: a retrospective cohort study

Purpose: Infective endocarditis (IE) is a severe condition with risk of recurrence. Oral microorganisms (OM) are frequently implicated as index pathogens, yet patient characteristics, bacteremia with OM and relapse bacteremia after completion of IE treatment remain poorly described among these patients. Methods: This descriptive single-center retrospective cohort study included patients hospitalized with possible or definite IE at Copenhagen University Hospital. Patients were stratified by index pathogen into an OM and non-OM group. Baseline characteristics were described, and bacteremia with OM were assessed up to three years after completion of IE treatment using Aalen-Johansen cumulative incidence functions. Also, relapse bacteremia was evaluated in both groups. Results: Of 686 patients, 171 (25%) patients were categorized into the OM group, of which 83% had viridans group streptococci as index IE pathogen. Patients in the OM group had a median age of 62 years [IQR 49, 72] vs. 68 [IQR 59, 75] in the non-OM group. They had more often congenital heart disease, but had less often diabetes, chronic kidney disease and cardiac implantable electronic devices. The relapse bacteremia rate was 2%, occurring exclusively in the non-OM group. The three-year cumulative incidence of bacteremia with OM was 2.6%, 95% CI 0.1–5.1 and 2.8%, 95% CI 1.2–4.5, p = 0.88, in the OM and non-OM group, respectively. Conclusions: IE caused by OM occurred in younger and healthier patients. Relapse bacteremia was low and only observed in the non-OM group. The three-year cumulative incidence of bacteremia with OM occurred at comparable low rates across both groups.