The role of Saccharibacteria (TM7) in the subginival microbiome as a predictor for secondary cardiovascular events

Background: The composition of the subgingival microbiota is of great importance in both oral and systemic diseases. However, a possible association of the oral microbiome and cardiovascular (CV) outcome has not yet been considered in a complex model. The primary objective of the study (DRKS-ID: DRKS00015776) was to assess differences in complex subgingival bacterial composition, depending on the CV outcome in patients undergoing Coronary Artery Bypass Grafting Surgery (CABG).

Material and methods: We conducted a longitudinal cohort study enrolling 102 CV patients. After a one-year follow-up, the postoperative outcome was evaluated applying MACCE (Major Adverse Cardiac and Cerebrovascular Events) criteria. The complex oral microbiome was evaluated depending on CV outcome. The mathematical data processing included Qiime 2 software workflow and DADA2 pipeline as well as Human Oral Microbiome Database (HOMD) and Greengenes database classification. For identifying biomarkers distinguishing patients suffering from secondary CV events, the Cox Proportional Hazard Model for survival analysis was applied.

Results: In total, 19,418 Operational Taxonomic Units (OTU) were mapped according to the HOMD and Greengenes database. No significant differences in alpha and beta diversity were linked to CV outcomes (Shannon index; Principal Coordinates Analysis). No biomarker predicting secondary CV events were identified applying the area under the receiver operating characteristic curve (AUC) model. However, in survival analysis, one biomarker of Saccharibacteria phylum (class: TM7-3, order: CW040, family: F16) was associated with the incidence of a secondary CV event (p = 0.016).

Conclusions: For the first time, a subgingival biomarker has been identified that supports a cardiovascular prognosis in CV patients undergoing coronary artery bypass grafting.