Bacterial Communities Associated with Atherosclerotic Plaques from Russian Individuals with Atherosclerosis

Abstract

Atherosclerosis is considered a chronic disease of the arterial wall and is the major cause of severe disease and death among individuals all over the world. Some recent studies have established the presence of bacteria in atherosclerotic plaque samples and suggested their possible contribution to the development of cardiovascular disease. The main objective of this preliminary pilot study was to better understand the bacterial diversity and abundance in human atherosclerotic plaques derived from common carotid arteries of individuals with atherosclerosis (Russian nationwide group) and contribute towards the further identification of a main group of atherosclerotic plaque bacteria by 454 pyrosequencing their 16S ribosomal RNA (16S rRNA) genes. The applied approach enabled the detection of bacterial DNA in all atherosclerotic plaques. We found that distinct members of the order Burkholderiales were present at high levels in all atherosclerotic plaques obtained from patients with atherosclerosis with the genus Curvibacter being predominant in all plaque samples. Moreover, unclassified Burkholderiales as well as members of the genera Propionibacterium and Ralstonia were typically the most significant taxa for all atherosclerotic plaques. Other genera such as Burkholderia, Corynebacterium and Sediminibacterium as well as unclassified Comamonadaceae, Oxalobacteraceae, Rhodospirillaceae, Bradyrhizobiaceae and Burkholderiaceae were always found but at low relative abundances of the total 16S rRNA gene population derived from all samples. Also, we found that some bacteria found in plaque samples correlated with some clinical parameters, including total cholesterol, alanine aminotransferase and fibrinogen levels. Finally, our study indicates that some bacterial agents at least partially may be involved in affecting the development of cardiovascular disease through different mechanisms.

Fig 1. Bacteria associated with atherosclerotic plaque samples (mean values).

Taxonomic classification of bacterial reads at (A) phylum level, (B) class level, (C) order level and (D) family level is demonstrated (data show more than 0.5%). Representatives accounting for less than 0.5% of all classified sequences are summarized in the group “others”.

Fig 2. PCoA plots of the bacterial communities distribution in atherosclerotic plaque samples based on the data received by pyrosequencing of 16S rRNA gene fragments.

(A) Unweighted Unifrac measurements. (B) Weighted Unifrac measurements (blue circles–men patients, red circles–women patients).

Fig 3. Heat map of the relative abundances of OTUs which differed between individual atherosclerotic plaque samples.