Metagenomic analysis of atheroma plaques for identification of microorganisms indicates presence of Toxoplasma gondii as a possible etiological agent.

Background: Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Vital organs like the heart are affected by the occlusion of blood vessels due to atherosclerotic plaque formation. However, the role of infectious agents has always been an essential subject of investigation. This study investigated the presence of microorganisms, including nanobacteria, in atherosclerotic plaques removed from human carotid arteries by microbiological and metagenomic examination.

Methods: Atheroma plaque samples were obtained from 20 patients with carotid artery stenosis who had atherectomy by surgery or percutaneous intervention. Nanobacteria were grown by culturing homogenates of the atheroma plaques. Whole genome sequencing was done for samples. Because of the high percentage of Toxoplasma gondii (T. gondii) DNA, PCR investigation was applied to detect T. gondii DNA in the samples.

Results: A molecular analysis of nanobacteria revealed them to be made of human proteins, supporting the theory that they are not living organisms. According to sequencing results, samples showed that more than 50 % of the metagenomic sequences belonged to Toxoplasma gondii. PCR investigation indicated that T. gondii DNA was positive in 8 (40 %) of 20 plaques.

Conclusions: Further evidence regarding the role of T. gondii in the etiology of plaque formation may help determine the strategy for prevention and treatment of infections in preventing atheroma plaque formation in the future.