Pathological Alterations in Human Blood Microbiome—An Updated Review

The main source of microorganisms in the blood is the intestinal and oral microflora through the route of atopobiosis. It is clear that the blood microbiome undergoes significant changes in response to various pathological conditions within the human body. In this review, we summarized data from studies of the human blood microbiome in diseases of the nervous system and cardiovascular, respiratory, liver, kidney, and metabolite disorders. Links between the blood microbiome and the above mentioned diseases are demonstrated. In support of this understanding, it is evident that analogous alterations in microbiome composition occur across various disease categories; however, the microbial signatures associated with the blood microbiome exhibit specificity. For instance, an elevated abundancy of Proteobacteria has been identified in cardiovascular, renal, and metabolic disorders. Conversely, while Firmicutes are found to be abundant in renal and metabolic conditions, their levels are diminished in cardiovascular diseases. Additionally, patients suffering from respiratory and liver ailments typically show a heightened presence of Bacteroidetes; notably, Flavobacterium is prevalent in respiratory diseases, whereas Enterobacteriaceae is associated with liver diseases. Hence, the human blood microbiome could be considered as a potential biomarker in certain diseases.