Next-generation sequencing reveals the presence of a rich bacterial microbiome in atherosclerotic coronary artery plaques. The Tampere Sudden Death Study

BackgroundMolecular microbial techniques have identified several DNA sequences from oral and gut bacteria in atherosclerotic plaques. The composition of the plaque microbiome has shown great heterogeneity due to varying DNA extraction and amplification methods, small size sample cohorts, and a low abundance of bacteria in plaques, leading to interference by contaminating bacterial sequences from laboratory chemicals. We used a novel next-generation sequencing (NGS) approach to analyze the entirety of bacterial DNAs found in coronary artery plaques in a unique prospective autopsy series of out-of-hospital deaths representing a cross-section of the general population. MethodsDNA was extracted from aseptically collected and frozen (-80 {degrees}C) atherosclerotic coronary plaque samples taken from the left anterior descending (LAD) coronary arteries of 202 victims of sudden out-of-hospital death included in the Tampere Sudden Death Study. Bacterial DNA was amplified using nested 16S rRNA PCR and sequenced. Amplicon sequence variants (ASVs) were inferred using the DADA2 approach. Taxonomy assignment of the sequences was accomplished using the Silva database (version 138).The presence of bacteria in coronary artery atherosclerotic plaques was confirmed by immunohistochemistry. ResultsASVs from 230 bacteria at the genus level occurring in humans were detected in the coronary plaques. The most common ASVs detected in almost all plaques belonged to the oral biofilm-producing bacteria Veillonella and Streptococcus, which, along with Prevotella, Lactobacillus, Clostridium, and Fusobacterium were the genera with the most ASV reads following nested PCR. The immunopositivity of oral streptococci and Veillonella occurred mainly as biofilm-like structures around calcific plaque areas and associated with the severity of atherosclerosis. ConclusionCoronary plaques harbor DNA sequences from dozens of mainly oral bacteria. However, only a few bacteria are so common that they likely have a role in the buildup of the microbiome inside a coronary artery atheroma.