Distinct Blood and Oral Microbiome Profiles Reveal Altered Microbial Composition and Functional Pathways in Myocardial Infarction Patients

Shengnan Lei ¹ Zhiqiang Li ¹ Jianye Zhou ¹ Linghong Zhu ¹ Zilong Zhang ² Xiaodong Xie ³ Xu Zhang ⁴ Ikram Khan ^5* Tuo Chen ⁶

• ¹ Northwest University for Nationalities, Lanzhou, Gansu Province, China
• ² Third People's Hospital of Qinghai Province, Xining, Qinghai Province, China
• ³ Lanzhou University, Lanzhou, Gansu Province, China
• ⁴ Department of Stomatology, General Hospital of Tibetan Military Command Lhasa, Lhasa, Tibet, China
• ⁵ Department of Genetics, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
• ⁶ State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou, Gansu Province, China

The circulating microbiome is an emerging concept in biomedical research, offering the potential for predictive biomarkers and pathogen screening. Evidence suggests that the translocation of predominant oral microbes shapes the composition of the blood microbiome in the circulatory system. Herein, we applied this concept to characterize the blood microbiome signature of the healthy controls and patients with myocardial infarction (MI) compared to the oral microbiome signature. We enrolled 20 participants, including 10 healthy controls and 10 patients with MI. Blood and Saliva samples were collected from each participant to analyse the association between blood and oral microbiome in MI patients using 16S rRNA gene sequencing. Our findings revealed that, compared to the oral microbiome, the blood microbiome exhibited significantly higher alpha diversity (p<0.05), while no statistical differences were observed in beta diversity metrics. The blood microbiome of MI patients was predominantly composed of the phyla Firmicutes, Bacteroidota, Actinobacteriota, genus Bacteroides, and depleted levels of Proteobacteria. While Firmicutes, Bacteroidota, Veillonella, and Prevotella_7 dominated the oral microbiome profile. LEfSe analysis found two distinct bacterial taxa in the blood, such as Actinobacteria in MI and Enterobacterales in the control group. At the same time, the oral microbiota was distinctly abundant to Rothia, Micrococcaceae, and Micrococcales in the healthy group, with no distinct taxa found in MI patients. Furthermore, the KEGG Annotated pathway showed significant alterations in the blood and oral microbiome functional prediction pathways between both groups. Moreover, the blood and oral microbiome signatures revealed a substantial correlation with demographic and clinical markers. Our study confirms that the blood contains a distinct microbiome with specific taxa and functional pathways rather than simply reflecting oral translocation. These findings highlight the potential role of the circulating microbiome in MI pathology and its link to clinical markers.