Human Blood Bacteriome: Eubiotic and Dysbiotic States in Health and Diseases

Abstract

The human gut microbiome is acknowledged as being associated with homeostasis and the pathogenesis of several diseases. Conventional culture techniques are limited in that they cannot culture the commensals; however, next-generation sequencing has facilitated the discovery of the diverse and delicate microbial relationship in body sites and blood. Increasing evidence regarding the blood microbiome has revolutionized the concept of sterility and germ theory in circulation. Among the types of microbial communities in the blood, bacteriomes associated with many health conditions have been thoroughly investigated. Blood bacterial profiles in healthy subjects are identified as the eubiotic blood bacteriome, whereas the dysbiotic blood bacteriome represents the change in bacterial characteristics in subjects with diseases showing deviations from the eubiotic profiles. The blood bacterial characteristics in each study are heterogeneous; thus, the association between eubiotic and dysbiotic blood bacteriomes and health and disease is still debatable. Thereby, this review aims to summarize and discuss the evidence concerning eubiotic and dysbiotic blood bacteriomes characterized by next-generation sequencing in human studies. Knowledge pertaining to the blood bacteriome will transform the concepts around health and disease in humans, facilitating clinical implementation in the near future.

Blood Stream Microbiota Dysbiosis Establishing New Research Standards in Cardio-Metabolic Diseases, A Meta-Analysis Study

“…Growing evidence suggests that bacteria or LPS binding protein (LBP) or LPS in the circulation cause systemic inflammation in cardio-metabolic diseases [ 17 ]. Several studies have added scientific reasoning and findings on the existence of a healthy human blood microbiome ( Table 2 ) [ 66 ]. Different studies have found bacterial 16S rDNA or rRNA in blood of healthy individuals [ 31 , 44 ], healthy blood donors [ 30 ], and various patient populations without overt infections [ 36 , 53 , 54 , 56 ] by advanced and reliable sequencing techniques.…”

Composition and changes of blood microbiota in adult patients with community-acquired sepsis: A pilot study from bench to bedside

“…The types of blood specimens could be grouped as whole blood, cellular components such as leukocytes, erythrocytes, the buffy coat, mononuclear cells and neutrophil granulocytes, and non-cellular components, such as serum, plasma, and extracellular vesicles. However, it is generally thought that analysis of whole blood might be the most representative specimen for blood microbiota, since it consists of all blood elements ( Suparan et al., 2022 ). According to published data, the most abundant phyla of whole blood “eubiotic” microbiota was Proteobacteria , followed by Firmicutes and Actinobacteria , but results are highly discordant on the genera level, identifying relevant microbiological variability, probably originating from oral and skin communities ( Paisse et al., 2016 ; Whittle et al., 2018 ) Lastly, comparative data showed that factors affecting the profiles of blood microbiota might be age, gender and geographic location ( D’Aquila et al., 2021 ; Panaiotov et al., 2021 ).…”

“…One review assessed that its three chief components, detected mainly by 16s rRNA gene sequencing at the phyla level, were Proteobacteria , Actinobacteria and Firmicutes , as they contributed to >70% of the blood microbiota, while Bacteroidetes , Fusobacteria , Cyanobacteria , Verrucomicrobia and Acidobacteria only constitute the minority. In contrast, Firmicutes and Bacteroidetes are the typical phyla of the human gut microbiome ( Suparan et al., 2022 ). Despite encouraging results, another review found that the main limitation to properly interpret the phylogenetic diversity of the healthy human blood microbiota lies in significant inter-research variability ( Castillo et al., 2019 ).…”

Environmental cadmium exposure alters the internal microbiota and metabolome of Sprague–Dawley rats

“…Blood microbiome has been a recent discovery, and specific bacterial species in blood have been reported to be associated with several infections and inflammation-related diseases ( 11 , 12 , 14 ). For example, an increased abundance of Sediminibacterium in the blood is associated with a heightened risk of developing type 2 diabetes mellitus (T2DM) ( 15 ).…”

“…Increased abundances of Proteobacteria phylum, Gammaproteobacteria class, and Enterobacteriaceae and Pseudomonadaceae families were found in the blood of patients with chronic kidney disease (CKD) ( 16 ). The primary source of blood microbiome has been reported to be microorganisms transferred from the gut or oral cavity ( 11 , 12 ). Cd exposure is known to trigger inflammation and disrupt intestinal permeability, allowing microbes to enter the blood circulation and inducing metabolic disorders ( 13 , 17 , 18 ).…”