Abstract
A survey and analytical assessment of the results of fundamental works on studying blood metagenome (set of all non-human DNA) is carried out. All works on determining bacterial DNA concentration in the whole blood of healthy people are reviewed. Detailed comparison of characteristics of 16S rRNA test (hereinafter 16S-test) and whole metagenome sequencing test (hereinafter WMS-test) is carried out and published in Supplement S1. One of main goals of this review is to identify the drawbacks and mistakes which the studied works contain, particularly to emphasize the crucial importance of determining total concentration of bacterial DNA for comparing patients' metagenomes with those of healthy people as well as for comparing patients' metagenomes with each other. Controlling the level and composition of contamination is equally important. The absence of high-quality contamination control at each step (or at certain steps) of the research significantly reduces the reliability of achieved results. The given review is the first attempt to analyze and systematize the results of blood metagenome studies, whose number has increased considerably in the last few years. The review has been carried out as part of preparation for implementing a project on complex studying metagenomes of whole blood and skin biopsies of psoriatic patients.
Highlights
The blood metagenome has been frequently identified for its various fractions, both for patients with various diseases, and for healthy people
The authors register a considerable decrease of genus Bifidobacterium representation at patients compared to HP (300 OTU on average), which correlates with the information on the positive role of this genus’ bacteria in intestine microbiome as well as on its possible role in preventing and reducing celiac disease severity
If determining total bacDNA concentration has been done, in the absence of contamination control there is still a problem of reliability of the received results, since it still remains unknown for which bacDNA concentration is considerably higher than contamination level, and for which bacDNA concentration does not exceed contamination level
Summary
The blood metagenome has been frequently identified for its various fractions, both for patients with various diseases, and for healthy people. In (13) blood plasma of patients with psoriatic arthritis was investigated; in 9 PP out of 19, bacDNA of Streptococcus pyogenes, Str. agalactiae, and Str. pneumoniae were found. Their presence was determined by the PCR method with specific primers for these species. The fact that bacDNA was not found in blood plasma in HP, and frequently in most PP (whereas researches of whole blood were not conducted), made it difficult to make any assertions about the role of its presence in blood in psoriasis pathogenesis.
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