The Healthy Human Blood Microbiome: Fact or Fiction?

Castillo, Diego; Rifkin, Riaan F.; Cowan, Don A.; Potgieter, Marnie

doi:10.3389/fcimb.2019.00148

Cited by 225 publications

(248 citation statements)

References 99 publications

(200 reference statements)

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“…We cannot determine whether the identified 16S rRNA gene sequences came from live, senescent or fragmented bacteria. Schierwagen et al were able to cultivate Staphylococcus and Acinetobacter (a group of environmental bacteria) using blood samples, which matched their findings by 16S rRNA gene sequencing and is in line with the numerous studies that identify living bacteria in the blood of healthy individuals by culture methods and microscopy 38 . However, given the chemical and mechanical stress that is inherent to digestion, and the fact that these patients did not display sepsis or any sign of bacterial infection, we speculate that the majority of the 16S rRNA sequences annotated in this study were from fragmented bacteria, which would facilitate translocation past the leaky gut barrier of participants with obesity.…”

Section: Discussionsupporting

confidence: 64%

Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity

et al. 2020

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Visceral obesity is a key risk factor for type 2 diabetes (T2D). Whereas gut dysbiosis appears to be instrumental for this relationship, whether gut-associated signatures translocate to extra-intestinal tissues and how this affects host metabolism remain elusive. Here we provide a comparative analysis of the microbial profile found in plasma, liver and in three distinct adipose tissues of individuals with morbid obesity. We explored how these tissue microbial signatures vary between individuals with normoglycaemia and those with T2D that were matched for body mass index. We identified tissue-specific signatures with higher bacterial load in the liver and omental adipose tissue. Gut commensals, but also environmental bacteria, showed tissueand T2D-specific compartmentalisation. T2D signatures were most evident in mesenteric adipose tissue, in which individuals with diabetes displayed reduced bacterial diversity concomitant with fewer Gram-positive bacteria, such as Faecalibacterium, as opposed to enhanced levels of typically opportunistic Gram-negative Enterobacteriaceae. Plasma samples of individuals with diabetes were similarly enriched in Enterobacteriaceae, including the pathobiont Escherichia-Shigella. Our work provides evidence for the presence of selective plasma and tissue microbial signatures in individuals with severe obesity and identifies new potential microbial targets and biomarkers of T2D.

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Section: Discussionsupporting

confidence: 64%

Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity

et al. 2020

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“…The penetration of bacteria through the gut wall leads to the increased presence of microorganisms or their components in the bloodstream, resulting in the activation of the immune system [13]. The concept of "healthy human blood microbiome" has been recently proposed, however, when the levels of bacteria or their derivatives in the bloodstream exceeds a certain threshold, this triggers systemic inflammation and sepsis (SIRS), which negatively affects all organs and tissues [14]. Therefore, it is believed that targeted modulation on microbiota or gut barriers can reduce the immune system activation and inflammatory response [15].…”

Section: Introductionmentioning

confidence: 99%

Microbiome-Metabolome Signature of Acute Kidney Injury

et al. 2020

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Intestinal microbiota play a considerable role in the host’s organism, broadly affecting its organs and tissues. The kidney can also be the target of the microbiome and its metabolites (especially short-chain fatty acids), which can influence renal tissue, both by direct action and through modulation of the immune response. This impact is crucial, especially during kidney injury, because the modulation of inflammation or reparative processes could affect the severity of the resulting damage or recovery of kidney function. In this study, we compared the composition of rat gut microbiota with its outcome, in experimental acute ischemic kidney injury and named the bacterial taxa that play putatively negative or positive roles in the progression of ischemic kidney injury. We investigated the link between serum creatinine, urea, and a number of metabolites (acylcarnitines and amino acids), and the relative abundance of various bacterial taxa in rat feces. Our analysis revealed an increase in levels of 32 acylcarnitines in serum, after renal ischemia/reperfusion and correlation with creatinine and urea, while levels of three amino acids (tyrosine, tryptophan, and proline) had decreased. We detected associations between bacterial abundance and metabolite levels, using a compositionality-aware approach—Rothia and Staphylococcus levels were positively associated with creatinine and urea levels, respectively. Our findings indicate that the gut microbial community contains specific members whose presence might ameliorate or, on the contrary, aggravate ischemic kidney injury. These bacterial taxa could present perspective targets for therapeutical interventions in kidney pathologies, including acute kidney injury.

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“…At the phylum level, we identified Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes. Once believed sterile, studies have shown healthy peripheral blood microbiomes typically include a nucleic acid signature of these phyla (5,32,46). Detection at the genus level produced a larger set of taxa, many of which (12 of 20) had inferred abundance significantly associated (FDR < 5%) with at least one host-related variable.…”

Section: Discussionmentioning

confidence: 99%

“…However, through use of culture-independent methods, evidence has emerged regarding the healthy human blood microbiome (5). The signature of the blood microbiome has provided insight into diseases such as schizophrenia (6), type 2 diabetes (7,8), chronic kidney disease (9) and liver fibrosis (10), and may provide a link to the microbiome in other tissues and diseases.…”

Section: Introductionmentioning

confidence: 99%

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Peripheral blood microbial signatures in COPD

Morrow

Castaldi

Chase

et al. 2020

Preprint

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Background:The human microbiome has a role in the development of human diseases. Individual microbiome profiles are highly personalized, though many species are shared. Understanding the relationship between the human microbiome and disease may inform future individualized treatments.Specifically, the blood microbiome, once believed sterile, may be a surrogate for some lung and gut microbial characteristics. We sought associations between the blood microbiome and lung-relevant host factors.Methods: Based on reads not mapped to the human genome, we detected microbial nucleic acid signatures in peripheral blood RNA-sequencing for 2,590 current and former smokers with and without chronic obstructive pulmonary disease (COPD) from the COPDGene study. We used the GATK microbial pipeline PathSeq to infer microbial profiles. We tested associations between the inferred profiles and lung disease relevant phenotypes and examined links to host gene expression pathways. Results:The four phyla with highest abundance across all subjects were Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. We observed associations between exacerbation phenotypes and the relative abundance of Staphylococcus, Acidovorax and Cupriavidus. The genus Flavobacterium was associated with emphysema and change in emphysema. Our host-microbiome interaction analysis revealed clustering of genera associated with emphysema, systemic inflammation, airway remodeling and exacerbations, through links to lung-relevant host pathways. Conclusions:This study is the first to identify a bacterial microbiome signature in the peripheral blood of current and former smokers. Understanding the relationships between the systemic microbial populations and lung disease severity may inform novel interventions and aid in the understanding of exacerbation phenotypes. Abstract word count: 246 COPD Foundation FundingCOPDGene is also supported by the COPD Foundation through contributions made to an Industry

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The Healthy Human Blood Microbiome: Fact or Fiction?

Cited by 225 publications

References 99 publications

Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity

Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity

Microbiome-Metabolome Signature of Acute Kidney Injury

Peripheral blood microbial signatures in COPD

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