Oral Microbiome in Infective Endocarditis: A Pilot Study

Objectives: The association between the oral microbiome and distant-site infections, such as infective endocarditis (IE), is poorly understood. IE can result from bacteremia caused by manipulation of gingival tissues. Our objective was to determine the oral microbiome profiles for patients who developed IE.

Methods: Oral samples of different sites (sub- and supragingival plaque, saliva, buccal mucosa, and dorsal tongue) were obtained from hospitalized patients with IE (IE group; N=5) and outpatients with cardiac conditions as controls (non-IE group; N=22). Oral microbiome profiles were determined using next generation sequencing of the bacterial 16S rRNA gene v1-v3 region. Non-metric multidimensional scaling (nMDS) and permutational multivariate analysis of variance (PERMANOVA, Monte-Carlo p<0.05) were used to determine differences in beta-diversity, based on relative abundance (RA) for all bacterial species detected and a subset of IE-associated species.

Results: We detected a total of 274 species, including 52 IE-associated, in the IE group compared to 394 species including 63 IE-associated in the non-IE group for all oral samples combined, corresponding to total of 431 species in IE and non-IE groups together. We detected 169 species (including 36 IE-associated) in subgingival plaque in the IE group and 323 species (including 58 IE-associated) in the non-IE group. Beta-diversity for all detected species or IE-associated species only, for sub- and supragingival plaque and saliva samples, differed between the IE group and non-IE group. Granulicatella adjacens was found with a higher RA in IE-group compared to non-IE group (p=0.0385, Mann-Whitney U-test). Additionally, nMDS showed that, based on microbiome profiles, non-IE patient samples formed a tight cluster while IE patient samples were dispersed.

Conclusions: Changes in microbiome profiles in the oral cavity might be characteristic of IE patients and may occur pre- and/or post-hospitalization. A larger patient cohort is needed to better characterize IE-associated species profiles in patients at risk for IE.