The Healthy Human Blood Microbiome: Fact or Fiction?

Metabarcoding using nanopore sequencing enables identification of diverse and zoonotic vector-borne pathogens from neglected regions: A case study investigating dogs from Bhutan

The diversity and prevalence of canine vector-borne pathogens (VBPs) in Bhutan have to date remained unexplored, whilst recent epidemiological surveys in other South Asian nations have found diseases caused by VBPs to be rife in local dog populations. Importantly, many of such VBPs can infect people as well, with a building body of evidence identifying potentially zoonotic rickettsial organisms infecting humans in Bhutan. Given the lack of data on canine pathogens in Bhutan we employed a suite of deep-sequencing metabarcoding methods using Oxford Nanopore Technologies' MinION™ device to holistically characterise the bacterial, apicomplexan and filarial worm blood-borne pathogens of dogs in the country's south. Of the 95 stray, owned and community dogs sampled 78% (95% CI = 69%-85%) were infected with at least one VBP. Pathogen species detected were highly diverse including the bacteria Mycoplasma haemocanis in 16% (95% CI: 10-24%), Ehrlichia canis in 4% (95% CI: 2-10%), Anaplasma platys in 2% (95% CI: 0.5-7%) of dogs as well as the zoonotic species Bartonella clarridgeiae in 1% (95% CI: 0.1-6%), a potentially novel Bartonella spp. and an Ehrlichia chaffeensis-like bacterium, both in 1% (95% CI: 0.1-6%) of dogs. The apicomplexan haemoparasites Hepatozoon canis in 62% (95% CI: 52-71%), Babesia gibsoni in 45% (95% CI: 36-55%) and Babesia vogeli in 3% (95% CI: 1-9%) of dogs were also detected. Finally, 5% (95% CI: 2-12%) of dogs were found to be infected with the filarioid Acanthocheilonema reconditum and 1% (95% CI: 0.1-6%) with zoonotic Dirofilaria sp. hongkongensis. One canine was found positive to the filarioid Setaria tundra, a species normally found infecting cervids. The elucidated diversity of VBP communities highlights the strength of assumption-free diagnostics, such as metabarcoding, in detecting rare, novel, and unexpected pathogens. This approach to identifying pathogen diversity is of critical importance when investigating regions and populations that have thus far been neglected, with the findings aiding the development of future One Health informed strategies for disease control.

Colorectal cancer-specific microbiome in peripheral circulation and cancer tissues

Introduction

Accumulating evidence has supported that gut microbiota and metabolite profiles play indispensable roles in the pathogenesis of colorectal cancer (CRC), which ranks as the third most common cancer and the second leading cause of cancer-related deaths worldwide. However, alterations in tumoral or circulating microbiomes in CRC remain incompletely understood. It has been well-documented that tissue or serum microbiomes with low microbial biomass could be screened by use of 2bRAD sequencing for microbiome (2bRAD-M) at the species resolution.

Methods

In order to validate the microbial biomarkers distinguishing CRC and the variations in microorganisms present in serum and tumors, we performed 2bRAD-M to characterize the microbiomes in serum and cancer tissues of CRC patients with and without lymph node or liver metastasis.

Results

The composition of dominated microbiota in serum was different from that of tissue samples, while the microbial community composition of tumors was similar to that of the tumor-adjacent tissues. The analysis of α-diversity and β-diversity has revealed notable variations in serum microbiota diversities in CRC patients, particularly those with liver metastasis. Multiple CRC-specific microbial species, such as Moraxella A cinereus, Flavobacterium sp001800905, and Acinetobacter albensis, were identified in serum. Complicated functions and KEGG pathways were also confirmed in CRC according to the metastasis status.

Discussion

This study has found significant alterations in the microbial compositions and diversities in CRC and CRC-specific microbial species in both circulation and cancer tissues, which may serve as promising biomarkers for the screening, diagnosis and prognosis prediction of CRC. In particular, CRC-specific bacterial taxa are promising markers, holding transformative potentials in establishing personalized screening and risk stratification, refining much earlier non-invasive diagnostic approaches, and enhancing diagnostic sensitivity.

Cell-Free Microbial DNA Analysis: Effects of Blood Plasma and Serum Quantity, Biobanking Protocols, and Isolation Kits

Recent studies highlight the presence of bacterial sequences in the human blood, suggesting potential clinical significance for circulating microbial signatures. These sequences could presumably serve in the diagnosis, prediction, or monitoring of various health conditions. Ensuring the similarity of samples before bacterial analysis is crucial, especially when combining samples from different biobanks prepared under varying conditions (such as different DNA extraction kits, centrifugation conditions, blood collection tubes, etc.). In this study, we aimed to analyze the impact of different sample collection and nucleic acid extraction criteria (blood collection tube, centrifugation, input volume, and DNA extraction kit) on circulating bacterial composition. Blood samples from four healthy individuals were collected into three different sample collection tubes: K2EDTA plasma tube, sodium citrate plasma tube, and gel tube for blood serum. Tubes were centrifugated at standard and double centrifugation conditions. DNA extraction was performed using 100, 200, and 500 μL plasma/serum input volumes. DNA extraction was performed using three different isolation kits: Norgen plasma/serum cell-free circulating DNA purification micro kit, Applied Biosystems MagMAX cell-free DNA isolation kit, and Qiagen QIAamp MinElute cell-free circulating DNA mini kit. All samples were subjected to 16S rRNA V1-V2 library preparation and sequencing. In total, 216 DNA and 18 water control samples were included in the study. According to PERMANOVA, PCoA, Mann-Whitney, and FDR tests the effect of the DNA extraction kit on the microbiota composition was the greatest, whereas the type of blood collection tube, centrifugation type, and sample input volume for the extraction had minor effects. Samples extracted with the Norgen DNA extraction kit were enriched with Gram-negative bacteria, whereas samples extracted with the Qiagen and MagMAX kits were enriched with Gram-positive bacteria. Bacterial profiles of samples prepared with the Qiagen and MagMAX DNA extraction kits were more similar, whereas samples prepared with the Norgen DNA extraction kit were significantly different from other groups.

Intratumoral Microbiome: Foe or Friend in Reshaping the Tumor Microenvironment Landscape?

The role of the microbiome in cancer and its crosstalk with the tumor microenvironment (TME) has been extensively studied and characterized. An emerging field in the cancer microbiome research is the concept of the intratumoral microbiome, which refers to the microbiome residing within the tumor. This microbiome primarily originates from the local microbiome of the tumor-bearing tissue or from translocating microbiome from distant sites, such as the gut. Despite the increasing number of studies on intratumoral microbiome, it remains unclear whether it is a driver or a bystander of oncogenesis and tumor progression. This review aims to elucidate the intricate role of the intratumoral microbiome in tumor development by exploring its effects on reshaping the multileveled ecosystem in which tumors thrive, the TME. To dissect the complexity and the multitude of layers within the TME, we distinguish six specialized tumor microenvironments, namely, the immune, metabolic, hypoxic, acidic, mechanical and innervated microenvironments. Accordingly, we attempt to decipher the effects of the intratumoral microbiome on each specialized microenvironment and ultimately decode its tumor-promoting or tumor-suppressive impact. Additionally, we portray the intratumoral microbiome as an orchestrator in the tumor milieu, fine-tuning the responses in distinct, specialized microenvironments and remodeling the TME in a multileveled and multifaceted manner.

The profile of blood microbiome in new-onset type 1 diabetes children

Blood microbiome signatures in patients with type 1 diabetes (T1D) remain unclear. We profile blood microbiome using 16S rRNA gene sequencing in 77 controls and 64 children with new-onset T1D, and compared it with the gut and oral microbiomes. The blood microbiome of patients with T1D is characterized by increased diversity and perturbed microbial features, with a significant increase in potentially pathogenic bacteria compared with controls. Thirty-six representative genera of blood microbiome were identified by random forest analysis, providing strong discriminatory power for T1D with an AUC of 0.82. PICRUSt analysis suggested that bacteria capable of inducing inflammation were more likely to enter the bloodstream in T1D. The overlap of the gut and oral microbiome with the blood microbiome implied potential translocation of bacteria from the gut and oral cavity to the bloodstream. Our study raised the necessity of further mechanistic investigations into the roles of blood microbiome in T1D.

Blood Microbiota and Its Products: Mechanisms of Interference with Host Cells and Clinical Outcomes

In healthy conditions, blood was considered a sterile environment until the development of new analytical approaches that allowed for the detection of circulating bacterial ribosomal DNA. Currently, debate exists on the origin of the blood microbiota. According to advanced research using dark field microscopy, fluorescent in situ hybridization, flow cytometry, and electron microscopy, so-called microbiota have been detected in the blood. Conversely, others have reported no evidence of a common blood microbiota. Then, it was hypothesized that blood microbiota may derive from distant sites, e.g., the gut or external contamination of blood samples. Alteration of the blood microbiota's equilibrium may lead to dysbiosis and, in certain cases, disease. Cardiovascular, respiratory, hepatic, kidney, neoplastic, and immune diseases have been associated with the presence of Gram-positive and Gram-negative bacteria and/or their products in the blood. For instance, lipopolysaccharides (LPSs) and endotoxins may contribute to tissue damage, fueling chronic inflammation. Blood bacteria can interact with immune cells, especially with monocytes that engulf microorganisms and T lymphocytes via spontaneous binding to their membranes. Moreover, LPSs, extracellular vesicles, and outer membrane vesicles interact with red blood cells and immune cells, reaching distant organs. This review aims to describe the composition of blood microbiota in healthy individuals and those with disease conditions. Furthermore, special emphasis is placed on the interaction of blood microbiota with host cells to better understand disease mechanisms.

Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges

Although the impact of the gut microbiome on health and disease is well established, there is controversy regarding the presence of microorganisms such as bacteria and their products in organs and tissues. However, recent contamination-aware findings of tissue-resident microbial signatures provide accumulating evidence in support of bacterial translocation in cardiometabolic disease. The latter provides a distinct paradigm for the link between microbial colonizers of mucosal surfaces and host metabolism. In this Perspective, we re-evaluate the concept of tissue-resident bacteria including their role in metabolic low-grade tissue and systemic inflammation. We examine the limitations and challenges associated with studying low bacterial biomass samples and propose experimental and analytical strategies to overcome these issues. Our Perspective aims to encourage further investigation of the mechanisms linking tissue-resident bacteria to host metabolism and their potentially actionable health implications for prevention and treatment.

Exertional Stress-induced Pathogenic Luminal Content Translocation - Friend or Foe?

The incidence of perturbed gastrointestinal integrity, as well as resulting systemic immune responses and gastrointestinal symptoms, otherwise known as exercised-induced gastrointestinal syndrome (EIGS), is common among individuals who partake in prolonged exercise. EIGS may cause the translocation of pathogenic material, including whole bacteria and bacterial endotoxins, from the lumen into circulation, which may progress into clinical consequences such as sepsis, and potentially subsequent fatality. However, further investigation is warranted to assess the possibility of food allergen and/or digestive enzyme luminal to circulatory translocation in response to exercise, and the clinical consequences. Findings from this narrative literature review demonstrate evidence that whole bacteria and bacterial endotoxins translocation from the gastrointestinal lumen to systemic circulation occurs in response to exercise stress, with a greater propensity of translocation occurring with accompanying heat exposure. It has also been demonstrated that food allergens can translocate from the lumen to systemic circulation in response to exercise stress and initiate anaphylaxis. To date, no research investigating the effect of exercise on the translocation of digestive enzymes from the lumen into systemic circulation exists. It is evident that EIGS and consequential pathogenic translocation presents life-threatening clinical implications, warranting the development and implementation of effective management strategies in at-risk populations.

No evidence on infectious DNA-based agents in pediatric acute lymphoblastic leukemia using whole metagenome shotgun sequencing

The etiology of pediatric acute lymphatic leukemia (ALL) is still unclear. Whole-metagenome shotgun sequencing of bone marrow samples in patients with treatment-naïve ALL (n=6) was performed for untargeted investigation of bacterial and viral DNA. The control group consisted of healthy children (n=4) and children with non-oncologic diseases (n=2) undergoing bone marrow sampling. Peripheral blood of all participants was investigated at the same time. After bioinformatical elimination of potential contaminants by comparison with the employed controls, no significant amounts of microbial or viral DNA were identified.

The microbiota in patients with interstitial cystitis/bladder pain syndrome: a systematic review

OBJECTIVE

To comprehensively review and critically assess the literature on microbiota differences between patients with interstitial cystitis (IC)/bladder pain syndrome (BPS) and normal controls and to provide clinical practice guidelines.

MATERIALS AND METHODS

In this systematic review, we evaluated previous research on microbiota disparities between IC/BPS and normal controls, as well as distinctions among IC/BPS subgroups. A comprehensive literature search was conducted across PubMed/MEDLINE, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials. Relevant studies were shortlisted based on predetermined inclusion and exclusion criteria, followed by quality assessment. The primary focus was identifying specific taxonomic variations among these cohorts.

RESULTS

A total of 12 studies met the selection criteria. Discrepancies were adjudicated by a third reviewer. The Newcastle-Ottawa Scale was used to assess study quality. Predominantly, the studies focused on disparities in urine microbiota between IC/BPS patients and normal controls, with one study examining gut microbiota differences between the groups, and two studies exploring vaginal microbiota distinctions. Unfortunately, analyses of discrepancies in other microbiota were limited. Our findings revealed evidence of distinct bacterial abundance variations, particularly involving Lactobacillus, alongside variations in specific metabolites among IC/BPS patients compared to controls.

CONCLUSIONS

Currently, there is evidence suggesting significant variations in the diversity and species composition of the urinary microbiota between individuals diagnosed with IC/BPS and control groups. In the foreseeable future, urologists should consider urine microbiota dysbiosis as a potential aetiology for IC, with potential clinical implications for diagnosis and treatment.

Blood and sputum microbiota composition in Afghan immigrants and Iranian subjects with pulmonary tuberculosis

Background and Objectives

TB infection is one of the most challengeable epidemiological issues. Complex interactions between microbiota and TB infection have been demonstrated. Alteration in microbial population during TB infection may act as a useful biomarker. The present study examined the microbiota patterns of blood and sputum samples collected from Afghan immigrants and Iranian patients with active TB.

Materials and Methods

Sixty active pulmonary TB patients were enrolled in the study. Blood and sputum samples were collected. To detect phylum bacterial composition in the blood and sputum samples, bacterial 16S rRNA quantification by Real-Time qPCR was performed.

Results

A significant decrease in Bacteroidetes in Iranian sputum and blood samples of Afghan immigrants and Iranian TB active subjects were seen. While, sputum samples of Afghan immigrants showed no significant differences in Bacteroidetes abundance among TB active and control. Firmicutes were also presented no significant difference between sputum samples of the two races. Actinobacteria showed a significant increase in Iranian and Afghan sputum samples while this phylum showed no significant abundance in Iranian and Afghan TB positive blood samples. Proteobacteria also showed an increase in sputum and blood samples of the two races.

Conclusion

An imbalance in Bacteroidetes and Firmicutes abundance may cause an alteration in the microbiota composition, resulting in dysregulated immune responses and resulting in the augmentation of opportunistic pathogens during TB infection, notably Proteobacteria and Actinobacteria. Evaluation of human microbiota under different conditions of TB infection can be critical to a deeper understanding of the disease control.

Racial Differences in Plasma Microbial Translocation and Plasma Microbiome, Implications in Systemic Lupus Erythematosus Disease Pathogenesis

OBJECTIVE

Black groups have increased prevalence and accelerated pathogenicity of systemic lupus erythematosus (SLE) compared to other ethnic/racial groups. The microbiome and systemic microbial translocation are considered contributing factors to SLE disease pathogenesis. However, racial differences in the plasma microbiome and microbial translocation in lupus remain unknown.

METHODS

In the current study, we investigated plasma levels of microbial translocation (lipopolysaccharide [LPS] and zonulin) and the plasma microbiome using microbial 16S RNA sequencing of Black and White patients with SLE and Black and White healthy controls.

RESULTS

Plasma microbial translocation was increased in Black patients versus in White patients and in patients with SLE versus healthy controls regardless of race. Compared to sex, age, and disease status, race had the strongest association with plasma microbiome differences. Black groups (Black controls and Black patients) had lower α-diversity than White groups (White controls and White patients) and more distinct β-diversity. Black and White patients demonstrated differences in plasma bacterial presence, including Staphylococcus and Burkholderia. Compared to White patients, Black patients had higher SLE Disease Activity Index (SLEDAI) scores and urinary protein levels as well as a trend for increased anti-double-stranded DNA (dsDNA) antibody levels consistent with the known increased severity of lupus in Black patients overall. Certain plasma bacteria at the genus level were identified that were associated with the SLEDAI score, urinary protein, and anti-dsDNA antibody levels.

CONCLUSION

This study reveals racial differences in both quality and quantity of plasma microbial translocation and identified specific plasma microbiome differences associated with SLE disease pathogenesis. Thus, this study may provide new insights into future potential microbiome therapies on SLE pathogenesis.

Molecular rapid diagnostic testing for bloodstream infections: Nanopore targeted sequencing with pathogen-specific primers

BACKGROUND

Nanopore sequencing, known for real-time analysis, shows promise for rapid clinical infection diagnosis but lacks effective assays for bloodstream infections (BSIs).

METHODS

We prospectively assessed the performance of a novel nanopore targeted sequencing (NTS) assay in identifying pathogens and predicting antibiotic resistance in BSIs, analyzing 387 blood samples from December 2021 to April 2023.

RESULTS

The positivity rate for NTS (69.5 %, 269/387) nearly matches that of metagenomic next-generation sequencing (mNGS) (74.7 %, 289/387; p = 0.128) and surpasses the positivity rate of conventional blood culture (BC) (33.9 %, 131/387; p < 0.01). Frequent pathogens detected by NTS included Klebsiella pneumoniae (n = 54), Pseudomonas aeruginosa (n = 36), Escherichia coli (n = 36), Enterococcus faecium(n = 30), Acinetobacter baumannii(n = 26), Staphylococcus aureus(n = 23), and Human cytomegalovirus (n = 37). Against a composite BSI diagnostic standard, NTS demonstrated a sensitivity and specificity of 84.0 % (95 % CI 79.5 %-87.7 %) and 90.1 % (95 % CI 81.7 %-88.5 %), respectively. The concordance between NTS and mNGS results (the percentage of total cases where both either detected BSI-related pathogens or were both negative) was 90.2 % (359/387), whereas the consistency between NTS and BC was only 60.2 % (233/387). In 80.6 % (50/62) of the samples with identical pathogens identified by both NTS tests and BCs, the genotypic resistance identified by NTS correlated with culture-confirmed phenotypic resistance. Using NTS, 95 % of samples can be tested and analyzed in approximately 7 h, allowing for early patient diagnosis.

CONCLUSIONS

NTS is rapid, sensitive, and efficient for detecting BSIs and drug-resistant genes, making it a potential preferred diagnostic tool for early infection identification in critically ill patients.

Molecular and serological diagnosis of multiple bacterial zoonoses in febrile outpatients in Garissa County, north-eastern Kenya

Bacterial zoonoses are diseases caused by bacterial pathogens that can be naturally transmitted between humans and vertebrate animals. They are important causes of non-malarial fevers in Kenya, yet their epidemiology remains unclear. We investigated brucellosis, Q-fever and leptospirosis in the venous blood of 216 malaria-negative febrile patients recruited in two health centres (98 from Ijara and 118 from Sangailu health centres) in Garissa County in north-eastern Kenya. We determined exposure to the three zoonoses using serological (Rose Bengal test for Brucella spp., ELISA for C. burnetti and microscopic agglutination test for Leptospira spp.) and real-time PCR testing and identified risk factors for exposure. We also used non-targeted metagenomic sequencing on nine selected patients to assess the presence of other possible bacterial causes of non-malarial fevers. Considerable PCR positivity was found for Brucella (19.4%, 95% confidence intervals [CI] 14.2-25.5) and Leptospira spp. (1.7%, 95% CI 0.4-4.9), and high endpoint titres were observed against leptospiral serovar Grippotyphosa from the serological testing. Patients aged 5-17 years old had 4.02 (95% CI 1.18-13.70, p-value = 0.03) and 2.42 (95% CI 1.09-5.34, p-value = 0.03) times higher odds of infection with Brucella spp. and Coxiella burnetii than those of ages 35-80. Additionally, patients who sourced water from dams/springs, and other sources (protected wells, boreholes, bottled water, and water pans) had 2.39 (95% CI 1.22-4.68, p-value = 0.01) and 2.24 (1.15-4.35, p-value = 0.02) times higher odds of exposure to C. burnetii than those who used unprotected wells. Streptococcus and Moraxella spp. were determined using metagenomic sequencing. Brucellosis, leptospirosis, Streptococcus and Moraxella infections are potentially important causes of non-malarial fevers in Garissa. This knowledge can guide routine diagnosis, thus helping lower the disease burden and ensure better health outcomes, especially in younger populations.

Characterizing the blood microbiota in healthy and febrile domestic cats via 16s rRNA sequencing

This study aimed to evaluate the blood bacterial microbiota in healthy and febrile cats. High-quality sequencing reads from the 16S rRNA gene variable region V3-V4 were obtained from genomic blood DNA belonging to 145 healthy cats, and 140 febrile cats. Comparisons between the blood microbiota of healthy and febrile cats revealed dominant presence of Actinobacteria, followed by Firmicutes and Proteobacteria, and a lower relative abundance of Bacteroidetes. Upon lower taxonomic levels, the bacterial composition was significantly different between healthy and febrile cats. The families Faecalibacterium and Kineothrix (Firmicutes), and Phyllobacterium (Proteobacteria) experienced increased abundance in febrile samples. Whereas Thioprofundum (Proteobacteria) demonstrated a significant decrease in abundance in febrile. The bacterial composition and beta diversity within febrile cats was different according to the affected body system (Oral/GI, systemic, skin, and respiratory) at both family and genus levels. Sex and age were not significant factors affecting the blood microbiota of febrile cats nor healthy ones. Age was different between young adult and mature adult healthy cats. Alpha diversity was unaffected by any factors. Overall, the findings suggest that age, health status and nature of disease are significant factors affecting blood microbiota diversity and composition in cats, but sex is not.

Associations of Gut and Circulating Microbiota with Circulating Vitamin D3, Type I Interferon, and Systemic Inflammation in Chronic Spontaneous Urticaria Patients

Objective

To analyze the associations of the gut and circulating microbiota with circulating vitamin D3 (VD3), type I interferon (IFNI), systemic inflammation, and clinical profiles in chronic spontaneous urticaria (CSU) patients.

Methods

A total of 36 CSU patients with VD3 insufficiency (VDI; serum 25(OH)VD3 <30 ng/mL) and 36 sex-, age-, and body mass index-matched CSU patients with non-VDI were enrolled. Fecal and serum bacteria were identified through 16S rRNA sequencing, and serum 25(OH)VD3 and inflammation biomarkers were assessed using ELISA kits. IFNI response was determined by measuring the stimulatory activity of serum on IFNI-stimulated response element in HEK293 cells in vitro with luciferase assays.

Results

Higher urticarial activity score over 7 days (UAS7), higher frequency of levocetirizine resistance, and more severe proinflammation but weaker IFNI response were observed in VDI than non-VDI patients (all P<0.05). IFNI response was strongly positively associated with serum 25(OH)VD3 level in both groups (P<0.001). Compared to non-VDI patients, abundance of the fecal genera Prevotella 9, Escherichia-Shigella, and Klebsiella was significantly increased, while Bacteroides, Faecalibacterium, and Agathobacter were remarkably reduced in VDI patients (all P<0.05). Burkholderia-Caballeronia-Paraburkholderia (40.95%), Acinetobacter (3.05%), and Aquabacterium (2.37%) were the top three bacteria in sera from VDI patients. Both serum 25(OH)VD3 level and IFNI response were positively associated with fecal Bacteroides in the two groups (P<0.05). In non-VDI patients, there were moderately positive associations between IFNI response and fecal Lachnoclostridium, unclassified_f__Lachnospiraceae, and Phascolarctobacterium and between serum 25(OH)VD3 level and fecal Lachnoclostridium (all P<0.01). Circulating microbiota in VDI patients was closely related only to proinflammation and UAS7 (both P<0.05).

Conclusion

Changes in gut but not circulating microbiota composition are associated with serum 25(OH)VD3 insufficiency and impaired IFNI homeostasis, which points to greater disease severity (UAS7) and systemic proinflammation in CSU patients.

The human microbiome and benign prostatic hyperplasia: Current understandings and clinical implications

The research of the human microbiome in the preceding decade has yielded novel perspectives on human health and diseases. Benign prostatic hyperplasia (BPH) is a common disease in middle-aged and elderly males, which negatively affects the life quality. Existing evidence has indicated that the human microbiome, including urinary, intra-prostate, gut, oral and blood microbiome may exert a significant impact on the natural progression of BPH. The dysbiosis of the microbiome may induce inflammation at either a local or systemic level, thereby affecting the BPH. Moreover, metabolic syndrome (MetS) caused by the microbiome can also be involved in the development of BPH. Additionally, alterations in the microbiome composition during the senility process may serve as another cause of the BPH. Here, we summarize the influence of human microbiome on BPH and explore how the microbiome is linked to BPH through inflammation, MetS, and senility. In addition, we propose promising areas of investigation and discuss the implications for advancing therapeutic approaches.

Re-visiting humoral constitutive antibacterial heterogeneity in bloodstream infections

Although cellular immunity has garnered much attention in the era of single-cell technologies, humoral innate immunity has receded in priority due to its presumed limited roles. Hence, despite the long-recognised bactericidal activity of serum-a functional characteristic of constitutive humoral immunity-much remains unclear regarding mechanisms underlying its inter-individual heterogeneity and clinical implications in bloodstream infections. Recent work suggests that the immediate antimicrobial effect of humoral innate immunity contributes to suppression of the excessive inflammatory responses to infection by reducing the amount of pathogen-associated molecular patterns. In this Personal View, we propose the need to re-explore factors underlying the inter-individual heterogeneity in serum antibacterial competence as a new approach to better understand humoral innate immunity and revisit the clinical use of measuring serum antibacterial activity in the management of bacterial bloodstream infections. Given the current emphasis on subtyping sepsis, a serum bactericidal assay might prove useful in defining a distinct sepsis endotype, to enable more personalised management.

Lung endothelium, tau, and amyloids in health and disease

Lung endothelia in the arteries, capillaries, and veins are heterogeneous in structure and function. Lung capillaries in particular represent a unique vascular niche, with a thin yet highly restrictive alveolar-capillary barrier that optimizes gas exchange. Capillary endothelium surveys the blood while simultaneously interpreting cues initiated within the alveolus and communicated via immediately adjacent type I and type II epithelial cells, fibroblasts, and pericytes. This cell-cell communication is necessary to coordinate the immune response to lower respiratory tract infection. Recent discoveries identify an important role for the microtubule-associated protein tau that is expressed in lung capillary endothelia in the host-pathogen interaction. This endothelial tau stabilizes microtubules necessary for barrier integrity, yet infection drives production of cytotoxic tau variants that are released into the airways and circulation, where they contribute to end-organ dysfunction. Similarly, beta-amyloid is produced during infection. Beta-amyloid has antimicrobial activity, but during infection it can acquire cytotoxic activity that is deleterious to the host. The production and function of these cytotoxic tau and amyloid variants are the subject of this review. Lung-derived cytotoxic tau and amyloid variants are a recently discovered mechanism of end-organ dysfunction, including neurocognitive dysfunction, during and in the aftermath of infection.

Distinct compositions and functions of circulating microbial DNA in the peripheral blood compared to fecal microbial DNA in healthy individuals

The crucial function of circulating microbial DNA (cmDNA) in peripheral blood is gaining recognition because of its importance in normal physiology and immunity in healthy individuals. Evidence suggests that cmDNA in peripheral blood is derived from highly abundant, translocating gut microbes. However, the associations with and differences between cmDNA in peripheral blood and the gut microbiome remain unclear. We collected blood, urine, and fecal samples from volunteers to compare their microbial information via 16S rDNA sequencing. The results revealed that, compared with gut microbial DNA, cmDNA in peripheral blood was associated with reduced diversity and a distinct microbiota composition. The cmDNA in the blood reflects the biochemical processes of microorganisms, including synthesis, energy conversion, degradation, and adaptability, surpassing that of fecal samples. Interestingly, cmDNA in blood showed a limited presence of DNA from anaerobes and gram-positive bacteria, which contrast with the trend observed in fecal samples. Furthermore, analysis of cmDNA revealed traits associated with mobile elements and potential pathologies, among others, which were minimal in stool samples. Notably, cmDNA analysis indicated similarities between the microbial functions and phenotypes in blood and urine samples, although greater diversity was observed in urine samples. Source Tracker analysis suggests that gut microbes might not be the main source of blood cmDNA, or a selective mechanism allows only certain microbial DNA into the bloodstream. In conclusion, our study highlights the composition and potential functions associated with cmDNA in peripheral blood, emphasizing its selective presence; however, further research is required to elucidate the mechanisms involved.IMPORTANCEOur research provides novel insights into the unique characteristics and potential functional implications of circulating microbial DNA (cmDNA) in peripheral blood. Unlike other studies that analyzed sequencing data from fecal or blood microbiota in different study cohorts, our comparative analysis of cmDNA from blood, urine, and fecal samples from the same group of volunteers revealed a distinct blood-specific cmDNA composition. We discovered a decreased diversity of microbial DNA in blood samples compared to fecal samples as well as an increased presence of biochemical processes microbial DNA in blood. Notably, we add to the existing knowledge by documenting a reduced abundance of anaerobes and gram-positive bacteria in blood compared to fecal samples according to the analysis of cmDNA and gut microbial DNA, respectively. This observation suggested that a potential selective barrier or screening mechanism might filter microbial DNA molecules, indicating potential selectivity in the translocation process which contrasts with the traditional view that cmDNA primarily originates from random translocation from the gut and other regions. By highlighting these differences, our findings prompt a reconsideration of the origin and role of cmDNA in blood circulation and suggest that selective processes involving more complex biological mechanisms may be involved.

No viable bacterial communities reside in the urinary bladder of cats with feline idiopathic cystitis

Urinary microbial diversities have been reported in humans according to sex, age and clinical status, including painful bladder syndrome/interstitial cystitis (PBS/IC). To date, the role of the urinary microbiome in the pathogenesis of PBS/IC is debated. Feline idiopathic cystitis (FIC) is a chronic lower urinary tract disorder affecting cats with similarities to PBS/IC in women and represents an important problem in veterinary medicine as its aetiology is currently unknown. In this study, the presence of a bacterial community residing in the urinary bladder of cats with a diagnosis of FIC was investigated. Nineteen cats with clinical signs and history of FIC and without growing bacteria in standard urine culture were included and urine collected with ultrasound-guided cystocentesis. Bacterial community was investigated using a culture-dependent approach consisted of expanded quantitative urine culture techniques and a culture-independent approach consisted of 16S rRNA NGS. Several methodological practices were adopted to both avoid and detect any contamination or bias introduced by means of urine collection and processing which could be relevant due to the low microbial biomass environment of the bladder and urinary tract, including negative controls analysis. All the cats included showed no growing bacteria in the urine analysed. Although few reads were originated using 16S rRNA NGS, a comparable pattern was observed between urine samples and negative controls, and no taxa were confidently classified as non-contaminant. The results obtained suggest the absence of viable bacteria and of bacterial DNA of urinary origin in the urinary bladder of cats with FIC.

Validated WGS and WES protocols proved saliva-derived gDNA as an equivalent to blood-derived gDNA for clinical and population genomic analyses

BACKGROUND

Whole exome sequencing (WES) and whole genome sequencing (WGS) have become standard methods in human clinical diagnostics as well as in population genomics (POPGEN). Blood-derived genomic DNA (gDNA) is routinely used in the clinical environment. Conversely, many POPGEN studies and commercial tests benefit from easy saliva sampling. Here, we evaluated the quality of variant call sets and the level of genotype concordance of single nucleotide variants (SNVs) and small insertions and deletions (indels) for WES and WGS using paired blood- and saliva-derived gDNA isolates employing genomic reference-based validated protocols.

METHODS

The genomic reference standard Coriell NA12878 was repeatedly analyzed using optimized WES and WGS protocols, and data calls were compared with the truth dataset published by the Genome in a Bottle Consortium. gDNA was extracted from the paired blood and saliva samples of 10 participants and processed using the same protocols. A comparison of paired blood-saliva call sets was performed in the context of WGS and WES genomic reference-based technical validation results.

RESULTS

The quality pattern of called variants obtained from genomic-reference-based technical replicates correlates with data calls of paired blood-saliva-derived samples in all levels of tested examinations despite a higher rate of non-human contamination found in the saliva samples. The F1 score of 10 blood-to-saliva-derived comparisons ranged between 0.8030-0.9998 for SNVs and between 0.8883-0.9991 for small-indels in the case of the WGS protocol, and between 0.8643-0.999 for SNVs and between 0.7781-1.000 for small-indels in the case of the WES protocol.

CONCLUSION

Saliva may be considered an equivalent material to blood for genetic analysis for both WGS and WES under strict protocol conditions. The accuracy of sequencing metrics and variant-detection accuracy is not affected by choosing saliva as the gDNA source instead of blood but much more significantly by the genomic context, variant types, and the sequencing technology used.

Detecting prokaryote-specific gene and other bacterial signatures in thrombi from patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Microbial infection has been associated with thrombogenesis. This study aimed to detect bacterium-specific genes and other signatures in thrombi from patients with acute ischemic stroke and to relate these signatures to clinical characteristics.

METHODS

Blood samples were collected before thrombectomy procedures, and thrombus samples were obtained during the procedure. Identification and classification of bacteria in the samples were accomplished using 16 S rRNA gene sequencing. Bacterium-specific structures were observed with transmission electron microscopy. Bacterium-specific biomarkers were detected through immunohistochemical staining.

RESULTS

16 S rRNA gene was detected in 32.1% of the thrombus samples from 81 patients. Bacillus (0.04% vs. 0.00046%, p = 0.003), Parabacteroides (0.20% vs. 0.09%, p = 0.029), Prevotella (1.57% vs. 0.38%, p = 0.010), Streptococcus (1.53% vs. 0.29%, p = 0.001), Romboutsia (0.18% vs. 0.0070%, p = 0.029), Corynebacterium (1.61% vs. 1.26%, p = 0.026) and Roseburia (0.53% vs. 0.05%, p = 0.005) exhibited significantly higher abundance in thrombi compared to arterial blood. Bacteria-like structures were observed in 22 (27.1%), while whole bacteria-like structures were observed in 7 (8.6%) thrombi under transmission electron microscopy. Immunohistochemical staining detected bacterium-specific monocyte/macrophage markers in 51 (63.0%) out of 81 thrombi. Logistic regression analysis indicated that alcohol consumption was associated with a higher bacteria burden in thrombi (odds ratio = 3.19; 95% CI, 1.10-9.27; p = 0.033).

CONCLUSION

Bacterial signatures usually found in the oral cavity and digestive tract were detected in thrombi from patients with ischemic stroke. This suggests a potential involvement of bacterial infection in the development of thrombosis. Long-term alcohol consumption may potentially enhance this possibility.

Predicting patient outcomes after treatment with immune checkpoint blockade: A review of biomarkers derived from diverse data modalities

Immune checkpoint blockade (ICB) therapy targeting cytotoxic T-lymphocyte-associated protein 4, programmed death 1, and programmed death ligand 1 has shown durable remission and clinical success across different cancer types. However, patient outcomes vary among disease indications. Studies have identified prognostic biomarkers associated with immunotherapy response and patient outcomes derived from diverse data types, including next-generation bulk and single-cell DNA, RNA, T cell and B cell receptor sequencing data, liquid biopsies, and clinical imaging. Owing to inter- and intra-tumor heterogeneity and the immune system's complexity, these biomarkers have diverse efficacy in clinical trials of ICB. Here, we review the genetic and genomic signatures and image features of ICB studies for pan-cancer applications and specific indications. We discuss the advantages and disadvantages of computational approaches for predicting immunotherapy effectiveness and patient outcomes. We also elucidate the challenges of immunotherapy prognostication and the discovery of novel immunotherapy targets.

Role of symbiotic microbiota dysbiosis in the progression of chronic kidney disease accompanied with vascular calcification

Background: Chronic kidney disease (CKD) is now globally recognized as a critical public health concern. Vascular calcification (VC) represents a significant risk factor for cardiovascular events in individuals with CKD. It is the accessible and precise diagnostic biomarkers for monitoring the progression of CKD and the concurrent VC are urgently needed. Methods: The adenine diet-induced CKD rat model was utilized to investigate chronic kidney injury, calcification in the kidney and thoracic aorta, and dysregulation of biochemical indices. Enzyme-linked immune sandwich assays were employed to analyze changes in calcification-related proteins. 16S rRNA sequencing was performed to delineate the microbiota characteristics in the gut and blood of CKD-afflicted rats. Additionally, transcriptome sequencing of kidney tissue was conducted to explore the relationship between CKD-associated microbiota features and alterations in kidney function. Results: The adenine diet-induced CKD inhibited body weight gain, and led to kidney injury, and pronounced calcification in kidney and thoracic aorta. The microbiota both in the gut and blood of these affected rats exhibited significantly lower alpha diversity and distinctive beta diversity than those in their healthy counterparts. CKD resulted in dysregulation of several biochemical indices (including elevated levels of creatinine, low-density lipoprotein-cholesterol, sodium, phosphorous, total cholesterol, and urea and decreased levels of albumin, calcium, lactate dehydrogenase, and total bilirubin). Moreover, it upregulated calcification-related factors (bone sialoprotein [BSP], Klotho, fibroblast growth factor [FGF]-23, and sclerostin [SOST]) and lipopolysaccharide (LPS). Notably, the increased Acinetobacter in the blood was positively associated with calcifications in the kidney and thoracic aorta, in addition to the positive correlation with gut microbiota. The enrichment of Acinetobacter was concurrent with increases in calcification factors (BSP, FGF-23, and SOST), LPS, and phosphorous. Furthermore, transcriptome sequencing revealed that the enrichment of Acinetobacter was positively correlated with the majority of upregulated genes and negatively correlated with downregulated genes involved in the mineral absorption pathway. Conclusion: Our findings, for the first time, underscore that dysbiosis of symbiotic microbiota, both in the gut and blood, is involved in the progression of CKD. Particularly, the enrichment of Acinetobacter in blood emerges as a potential risk factor for CKD and its accompanying VC.

Peptoniphilus gorbachii alleviates collagen-induced arthritis in mice by improving intestinal homeostasis and immune regulation

Introduction

The intricate connection between gut microbiota and rheumatoid arthritis (RA) pathogenesis has gained prominence, although the specific microbial species contributing to RA development remain largely unknown. Recent studies have sought to comprehensively explore alterations in the human microbiome, focusing on identifying disease-related microbial species through blood analysis. Consequently, this study aimed to identify RA-associated microbial species using a serum microbial array system and to investigate the efficacy and underlying mechanisms of potential microbial species for RA treatment.

Methods

Serum immunoglobulin M levels against 384 intestinal microbial species were assessed using a microbial microarray in patients with RA and healthy individuals. We investigated the therapeutic potential of the identified microbial candidate regarding arthritis development, immune responses, gut barrier function, and gut microbiome using a collagen-induced arthritis (CIA) mouse model.

Results

Our findings revealed significant alterations in antibody levels against 36 microbial species in patients with RA compared to healthy individuals. Notably, the antibody levels against Peptoniphilus gorbachii (PG) were decreased in patients with RA and exhibited an inverse correlation with RA disease activity. In vitro experiments demonstrated that PG produced acetate and butyrate, while exhibiting anti-inflammatory properties. In CIA mice, PG administration suppressed arthritis symptoms, reduced the accumulation of inflammatory monocytes in the mesenteric lymph nodes, and downregulated gene expression of pro-inflammatory cytokines in the ileum. Additionally, PG supplementation restored intestinal barrier integrity and partially resolved gut microbial dysbiosis in CIA mice. The fecal microbiota in PG-treated mice corresponded to improved intestinal barrier integrity and reduced inflammatory responses.

Conclusion

This study highlights the potential of serum-based detection of anti-microbial antibodies to identify microbial targets at the species level for RA treatment. Moreover, our findings suggest that PG, identified through the microbial microarray analysis, holds therapeutic potential for RA by restoring intestinal barrier integrity and suppressing the immunologic response associated with RA.

Blood microbial analyses reveal long-term effects of SARS-CoV-2 infection on patients who recovered from COVID-19

OBJECTIVE

Few symptoms persist for a long time after patients recover from COVID-19, called "long COVID". We explored the potential microbial risk factors for COVID-19 for a deeper understanding and assistance in the follow-up treatment of these sequelae.

METHODS

Microbiome re-annotation was performed using whole blood RNA-Seq data collected from recovered COVID-19 patients and healthy controls at multiple time points. Subsequently, a series of downstream analyses were conducted to reveal the microbial characteristics of patients who recovered from SARS-CoV-2 infection.

RESULTS

The blood microbiome at 12 weeks post-infection was most evidently disturbed, including an increasing ratio of Bacillota/Bacteroidota and a higher microbial alpha diversity. In addition, a group of pathogenic microbes at 12 weeks post-infection were identified, including Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, which were positively associated with host genes involved in immune regulatory and olfactory transduction pathways. Several microbes, such as Streptococcus pneumoniae were associated with infiltrating immune cells, such as M2 macrophages.

CONCLUSION

This study provides insights into the relationship between the blood microbiome and COVID-19 sequelae. Several pathogenic microbes were enriched in recovered COVID-19 patients and thus affected host genes participating in the immune and olfactory transduction pathways, which play critical roles in COVID-19 sequelae.

Microbiome analysis of circulating bacterial extracellular vesicles in obsessive-compulsive disorder

AIM

The present study examined the microbiome abundance and composition of drug-naive or drug-free patients with obsessive-compulsive disorder (OCD) compared with healthy controls. In addition, in the OCD group, the microbiome composition was compared between early-onset and late-onset OCD.

METHODS

Serum samples were collected from 89 patients with OCD and 107 age- and sex-matched healthy controls. Bacterial DNA was isolated from bacteria-derived extracellular vesicles in serum and then amplified and quantified using primers specific to the V3-V4 hypervariable region of the 16S ribosomal RNA gene. The 16S ribosomal DNA gene amplicon sequencing was performed.

RESULTS

The pooled estimate showed that α-diversity was significantly reduced in patients with OCD compared with that in healthy controls (PShannon  = 0.00015). In addition, a statistically significant difference was observed in β-diversity between patients with OCD and healthy controls at the order (P = 0.012), family (P = 0.003), genus (P < 0.001), and species (P = 0.005) levels. In the microbiome composition, Pseudomonas, Caulobacteraceae (f), Streptococcus, Novosphingobium, and Enhydrobacter at the genus level were significantly less prevalent in patients with OCD than in controls. In addition, among patients with OCD, the microbial composition in the early-onset versus late-onset types was significantly different with respect to the genera Corynebacterium and Pelomonas.

CONCLUSION

The present study showed an aberrant microbiome in patients with OCD, suggesting a role of the microbiota-brain interaction in the pathophysiology of OCD. Further longitudinal studies with larger sample sizes adjusting for various confounders are warranted.

Characterization of markers, functional properties, and microbiome composition in human gut-derived bacterial extracellular vesicles

Past studies have confirmed the etiologies of bacterial extracellular vesicles (BEVs) in various diseases, including inflammatory bowel disease (IBD) and colorectal cancer (CRC). This study aimed to investigate the characteristics of stool-derived bacterial extracellular vesicles (stBEVs) and discuss their association with stool bacteria. First, three culture models - gram-positive (G+)BcBEVs (from B.coagulans), gram-negative (G-)EcBEVs (from E.coli), and eukaryotic cell-derived EVs (EEV, from Colo205 cell line) - were used to benchmark various fractions of stEVs separated from optimized density gradient approach (DG). As such, WB, TEM, NTA, and functional assays, were utilized to analyze properties and distribution of EVs in cultured and stool samples. Stool samples from healthy individuals were interrogated using the approaches developed. Results demonstrated successful separation of most stBEVs (within DG fractions 8&9) from stEEVs (within DG fractions 5&6). Data also suggest the presence of stBEV DNA within vesicles after extraction of BEV DNA and DNase treatment. Metagenomic analysis from full-length (FL) region sequencing results confirmed significant differences between stool bacteria and stBEVs. Significantly, F8&9 and the pooled sample (F5-F9) exhibited a similar microbial composition, indicating that F8&9 were enriched in most stBEV species, primarily dominated by Firmicutes (89.6%). However, F5&6 and F7 still held low-density BEVs with a significantly higher proportion of Proteobacteria (20.5% and 40.7%, respectively) and Bacteroidetes (24% and 13.7%, respectively), considerably exceeding the proportions in stool and F8&9. Importantly, among five healthy individuals, significant variations were observed in the gut microbiota composition of their respective stBEVs, indicating the potential of stBEVs as a target for personalized medicine and research.

Abnormal blood microbiota profiles are associated with inflammation and immune restoration in HIV/AIDS individuals

IMPORTANCE

The characteristics of blood microbiota in HIV-infected individuals and their relevance to disease progression are still unknown, despite alterations in gut microbiota diversity and composition in HIV-infected individuals. Here, we present evidence of increased blood microbiota diversity in HIV-infected individuals, which may result from gut microbiota translocation. Also, we identify a group of microbes, Porphyromonas gingivalis, Prevotella sp. CAG:5226, Eubacterium sp. CAG:251, Phascolarctobacterium succinatutens, Anaerobutyricum hallii, Prevotella sp. AM34-19LB, and Phocaeicola plebeius, which are linked to poor immunological recovery. This work provides a scientific foundation toward therapeutic strategies targeting blood microbiota for immune recovery of HIV infection.

Sensitizing cancer cells to immune checkpoint inhibitors by microbiota-mediated upregulation of HLA class I

Recent data have shown that gut microbiota has a major impact on the clinical response to immune checkpoint inhibitors (ICIs) in the context of solid tumors. ICI-based therapy acts by unlocking cognate cytotoxic T lymphocyte (CTL) effector responses, and increased sensitivity to ICIs is due to an enhancement of patients' tumor antigen (TA)-specific CTL responses. Cancer clearance by TA-specific CTL requires expression of relevant TAs on cancer cells' HLA class I molecules, and reduced HLA class I expression is a common mechanism used by cancer cells to evade the immune system. Here, we show that metabolites released by bacteria, in particular, phytosphingosine, can upregulate HLA class I expression on cancer cells, sensitizing them to TA-specific CTL lysis in vitro and in vivo, in combination with immunotherapy. This effect is mediated by postbiotic-induced upregulation of NLRC5 in response to upstream MYD88-NF-κB activation, thus significantly controlling tumor growth.

Efficient filter-in-centrifuge separation of low-concentration bacteria from blood

Separating bacteria from infected blood is an important step in preparing samples for downstream bacteria detection and analysis. However, the extremely low bacteria concentration and extremely high blood cell count make efficient separation challenging. In this study, we introduce a method for separating bacteria from blood in a single centrifugation step, which involves sedimentation velocity-based differentiation followed by size-based cross-flow filtration over an inclined filter. Starting from 1 mL spiked whole blood, we recovered 32 ± 4% of the bacteria (Escherichia coli, Klebsiella pneumonia, or Staphylococcus aureus) within one hour while removing 99.4 ± 0.1% of the red blood cells, 98.4 ± 1.4% of the white blood cells, and 90.0 ± 2.6% of the platelets. Changing the device material could further increase bacteria recovery to >50%. We demonstrated bacterial recovery from blood spiked with 10 CFU mL-1. Our simple hands-off efficient separation of low-abundant bacteria approaches clinical expectations, making the new method a promising candidate for future clinical use.

Metagenomic characterization of the microbiomes in five different body habitats of otherwise healthy individuals with periodontal disease

Introduction

Recent studies have proposed several plausible mechanisms supporting the association between periodontal disease and systemic disease. However, characterizing the microbial communities in individuals with periodontal disease before onset of other diseases is an important first step in determining how the altered microbial state contributes to disease progression. This study established microbiome profiles for five body habitats of carefully selected, otherwise healthy individuals with periodontal disease.

Methods

Blood, oral (buccal mucosa, dental plaque, and saliva), and stool samples were collected from ten healthy subjects with periodontal disease. Using 16S rRNA metagenomics, the taxonomic and functional compositions of microbiomes were investigated.

Results

The most predominant phylum in blood and stool was Bacillota. Pseudomonadota accounted for the largest proportion of microbes in the buccal mucosa and saliva, whereas Bacteroidota were the most prevalent in dental plaque. Differential abundance analysis revealed that 12 phyla and 139 genera were differentially abundant between body habitats. Comparison of alpha diversity showed that the blood microbiome has the most diverse community close to neither oral nor stool microbiomes. We also predicted the functional configurations of the microbiome in otherwise healthy subjects with periodontal disease. Principal coordinate analysis based on functional abundance revealed distinct clustering of the microbial communities between different body habitats, as also observed for taxonomic abundance. In addition, 13 functional pathways, including lipopolysaccharide biosynthesis, glutathione metabolism, and proteasome, showed differential expression between habitats.

Discussion

Our results offer insight into the effects of the microbiome on systemic health and disease in people with periodontal disease.

Are gut dysbiosis, barrier disruption, and endotoxemia related to adipose tissue dysfunction in metabolic disorders? Overview of the mechanisms involved

Recently, compelling evidence points to dysbiosis and disruption of the epithelial intestinal barrier as major players in the pathophysiology of metabolic disorders, such as obesity. Upon the intestinal barrier disruption, components from bacterial metabolism and bacteria itself can reach peripheral tissues through circulation. This has been associated with the low-grade inflammation that characterizes obesity and other metabolic diseases. While circulating bacterial DNA has been postulated as a common feature of obesity and even type 2 diabetes, almost no focus has been given to the existence and effects of bacteria in peripheral tissues, namely the adipose tissue. As a symbiont population, it is expected that gut microbiota modulate the immunometabolism of the host, thus influencing energy balance mechanisms and inflammation. Gut inflammatory signals cause direct deleterious inflammatory responses in adipose tissue and may also affect key gut neuroendocrine mechanisms governing nutrient sensing and energy balance, like incretins and ghrelin, which play a role in the gut-brain-adipose tissue axis. Thus, it is of major importance to disclose how gut microbiota and derived signals modulate neuroendocrine and inflammatory pathways, which contribute to the dysfunction of adipose tissue and to the metabolic sequelae of obesity and related disorders. This review summarizes the current knowledge regarding these topics and identifies new perspectives in this field of research, highlighting new pathways toward the reduction of the inflammatory burden of metabolic diseases.

The Impact of a 24-h Low and High Fermentable Oligo- Di- Mono-Saccharides and Polyol (FODMAP) Diet on Plasma Bacterial Profile in Response to Exertional-Heat Stress

Exertional-heat stress (EHS) compromises intestinal epithelial integrity, potentially leading to the translocation of pathogenic agents into circulation. This study aimed to explore the impact of EHS on the systemic circulatory bacterial profile and to determine the impact of a short-term low (LFOD) and high (HFOD) fermentable oligo- di- mono-saccharide and polyol dietary intervention before EHS on this profile. Using a double-blind randomized cross-over design, thirteen endurance runners (n = 8 males, n = 5 females), with a history of exercise-associated gastrointestinal symptoms (Ex-GIS), consumed a 24 h LFOD and HFOD before 2 h running at 60% V.O2max in 35.6 °C. Blood and fecal samples were collected pre-EHS to determine plasma microbial DNA concentration, and sample bacteria and short chain fatty acid (SCFA) profiles by fluorometer quantification, 16S rRNA amplicon gene sequencing, and gas chromatography, respectively. Blood samples were also collected post-EHS to determine changes in plasma bacteria. EHS increased plasma microbial DNA similarly in both FODMAP trials (0.019 ng·μL-1 to 0.082 ng·μL-1) (p < 0.01). Similar pre- to post-EHS increases in plasma Proteobacteria (+1.6%) and Firmicutes (+0.6%) phyla relative abundance were observed in both FODMAP trials. This included increases in several Proteobacteria genus (Delftia and Serratia) groups. LFOD presented higher fecal Firmicutes (74%) and lower Bacteroidota (10%) relative abundance pre-EHS, as a result of an increase in Ruminococcaceae and Lachnospiraceae family and respective genus groups, compared with HFOD (64% and 25%, respectively). Pre-EHS plasma total SCFA (p = 0.040) and acetate (p = 0.036) concentrations were higher for HFOD (188 and 178 μmol·L-1, respectively) vs. LFOD (163 and 153 μmol·L-1, respectively). Pre-EHS total fecal SCFA concentration (119 and 74 μmol·g-1; p < 0.001), including acetate (74 and 45 μmol·g-1; p = 0.001), butyrate (22 and 13 μmol·g-1; p = 0.002), and propionate (20 and 13 μmol·g-1; p = 0.011), were higher on HFOD vs LFOD, respectively. EHS causes the translocation of whole bacteria into systemic circulation and alterations to the plasma bacterial profile, but the FODMAP content of a 24 h diet beforehand does not alter this outcome.

Molecular Characterisation of Blood Microbiome in Patients with Ankylosing Spondylitis and Healthy Controls

Background

In human and animal studies, ankylosing spondylitis (AS) has been increasingly linked to changes in the microbial inhabitants in the human body (microbiome). These studies have primarily now concentrated on the microbial communities that live in the gastrointestinal tract. However, evidence suggests that various molecular techniques can be used to detect microbial DNA in blood circulation. This DNA might be an unknown reservoir of biomarkers with the potential to track alterations in the microbiomes of remote locations, such as the gut. To this end, we compared the presence and identity of microbial DNA in blood samples taken from ankylosing spondylitis patients to healthy control subjects by amplifying and sequencing the bacterial 16S rRNA variable region four.

Methods

The study's design is a case study based on the presence and identity of bacterial DNA in the blood of Ankylosing spondylitis (AS) patients (n = 10) and healthy control subjects (n = 10) was investigated by amplifying and sequencing the bacterial 16S rRNA gene. Blood concentrations of the cytokines TNF alpha, IL-17A, and IL-23 were determined by the Human Magnetic Luminex Screening, and data were analysed using an Unpaired T-test.

Results

Using PCR amplification, 8 of 10 AS patients (80%) and 8 of 10 healthy control samples (80%) had microbial 16S rRNA in their blood. At the phylum level, Proteobacteria (Control = 48.5%, AS = 52%), Firmicutes (Control = 27.8%, AS = 26.1%), Actinobacteria (Control = 15.4%, AS = 10.7%), and Bacteroidetes (Control = 6.5%, AS = 10%) dominated the blood microbiome. A two-tailed Mann-Whitney test found that Ankylosing Spondylitis was associated with significantly elevated Bacteroides (P < 0.05), Prevotella (P < 0.001), and Micrococcus (P < 0.01), and significantly reduced levels of Corynebacterium 1 (P < 0.001), Gemella (P < 0.01), and Alloprevotella (P < 0.05), compared to healthy controls. Additionally, it was shown that the presence of the Prevotella genus was highly positively correlated with higher levels of TNF-alpha (P < 0.05; r = 0.8) in AS patients' blood.

Conclusion

This article reveals that a blood microbiome exists in healthy individuals and identifies particular taxa modulated in disease. These blood-derived signatures indicate that this field needs more research and may be helpful as disease biomarkers.

Characterizing the blood microbiota of omnivorous and frugivorous bats (Chiroptera: Phyllostomidae) in Casanare, eastern Colombia

Bats are known reservoirs of seemingly-innocuous pathogenic microorganisms (including viruses, bacteria, fungi, and protozoa), which are associated with triggering disease in other zoonotic groups. The taxonomic diversity of the bats' microbiome is likely associated with species-specific phenotypic, metabolic, and immunogenic capacities. To date, few studies have described the diversity of bat blood microbial communities. Then, this study used amplicon-based next generation sequencing of the V4 hypervariable region of the 16S-rRNA gene in blood samples from omnivorous (n = 16) and frugivorous (n = 9) bats from the department of Casanare in eastern Colombia. We found the blood microbiota in bats to be composed of, among others, Bartonella and Mycoplasma bacterial genera which are associated with various disease phenotypes in other mammals. Furthermore, our results suggest that the bats' dietary habits might determine the composition and the persistence of some pathogens over others in their bloodstream. This study is among the first to describe the blood microbiota in bats, to reflect on co-infection rates of multiple pathogens in the same individual, and to consider the influence of diet as a factor affecting the animal's endogenous microbial community.

CRP in Outpatients with Inflammatory Bowel Disease Is Linked to the Blood Microbiota

The circulation is a closed system that has been assumed to be free from bacteria, but evidence for the existence of a low-density blood microbiota is accumulating. The present study aimed to map the blood microbiota of outpatients with Crohn's disease (CD) or with ulcerative colitis (UC) by 16S metagenomics. A diverse microbiota was observed in the blood samples. Regardless of the type of disease, the alpha diversity of the microbiota was positively associated with C-reactive protein (CRP). The blood microbiota had a surprisingly high proportion of Proteobacteria in comparison with human oral and colonic microbiotas. There was no clear difference in the overall pattern of the microbiota between CD and UC. A non-template control (NTC) was included in the whole process to control for the potential contamination from the environment and reagents. Certain bacterial taxa were concomitantly detected in both blood samples and NTC. However, Acinetobacter, Lactobacillus, Thermicanus and Paracoccus were found in blood from both CD and UC patients but not in NTC, indicating the existence of a specific blood-borne microbiota in the patients. Achromobacter dominated in all blood samples, but a minor amount was also found in NTC. Micrococcaceae was significantly enriched in CD, but it was also detected in high abundance in NTC. Whether the composition of the blood microbiota could be a marker of a particular phenotype in inflammatory bowel disease (IBD) or whether the blood microbiota could be used for diagnostic or therapeutic purposes deserves further attention.

Exploration of the interplay between spatially distinct microbial habitats through comparative analysis

Objectives

The oral microbiome is closely associated with systemic diseases, indicating the presence of bacteremia and inflammatory mediators in the systemic circulation. Our research aims to investigate the relationship between the oral microbiome and other microbial habitats.

Methods

We analyzed 180 specimens from 36 patients, including saliva, buccal swab, plaque, stool, and blood samples from a healthy group (Non_PD, n = 18) and a periodontitis group (PD, n = 18). The final analysis included 147 specimens, with varying sample sizes for each group. Metagenomic analysis was performed using prokaryotic 16S rRNA on the MiSeq platform (Illumina).

Results

PD saliva showed significant richness differences (P's < 0.05), similar to plaque. Buccal swabs had slight variations. Microbial network analysis revealed altered microbial interactions in the PD group, with decreased interactions in saliva and buccal swabs, and increased interactions in plaque. In our analysis of nine specimens where all paired habitat samples could be analyzed, microorganisms linked to oral periodontitis were found in sterile blood samples, resembling the oral cavity's composition.

Conclusions

Microbiome differences should consider overall microbial-environment interactions, alongside diversity and richness. Our data cautiously suggest that disease-related changes in the salivary microbiome may be reflected in blood specimens through the oral-blood axis.

The Diagnostic Potential of the Human Blood Microbiome: Are We Dreaming or Awake?

Human blood has historically been considered a sterile environment. Recently, a thriving microbiome dominated by Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes phyla was detected in healthy blood. The localization of these microbes is restricted to some blood cell populations, particularly the peripheral blood mononuclear cells and erythrocytes. It was hypothesized that the blood microbiome originates from the skin-oral-gut axis. In addition, many studies have evaluated the potential of blood microbiome dysbiosis as a prognostic marker in cardiovascular diseases, cirrhosis, severe liver fibrosis, severe acute pancreatitis, type 2 diabetes, and chronic kidney diseases. The present review aims to summarize current findings and most recent evidence in the field.

Body Size Poorly Predicts Host-Associated Microbial Diversity in Wild Birds

The composition and diversity of avian microbiota are shaped by many factors, including host ecologies and environmental variables. In this study, we examine microbial diversity across 214 bird species sampled in Malawi at five major body sites: blood, buccal cavity, gizzard, intestinal tract, and cloaca. Microbial community dissimilarity differed significantly across body sites. Ecological theory predicts that as area increases, so does diversity. We tested the hypothesis that avian microbiota diversity is correlated with body size, used as a proxy for area, using comparative phylogenetic methods. Using Pagel's lambda, we found that few microbial diversity metrics had significant phylogenetic signals. Phylogenetic generalized least squares identified a significant but weak negative correlation between host size and microbial diversity of the blood and a similarly significant but weakly positive correlation between the cloacal microbiota and host size among birds within the order Passeriformes. Phylosymbiosis, or a congruent branching pattern between host phylogeny and their associated microbiota similarity, was tested and found to be weak or not significant in four of the body sites with sufficient sample size (blood, buccal, cloaca, and intestines). Taken together, these results suggest that the avian microbiome is highly variable, with microbiota diversity demonstrating few clear associations with bird size. Finally, the blood microbiota have a unique relationship with host size. IMPORTANCE All animals coexist and interact with microorganisms, including bacteria, archaea, microscopic eukaryotes, and viruses. These microorganisms can have an enormous influence on the biology and health of macro-organisms. However, the general rules that govern these host-associated microbial communities are poorly described, especially in wild animals. In this paper, we investigate the microbial communities of over 200 species of birds from Malawi and characterize five body site bacterial microbiota in depth. Because the evolutionary relationships of the host underlie the relationship between any host-associated microbiota relationships, we use phylogenetic comparative methods to account for this relationship. We find that the size of a host (the bird) and the diversity and composition of the microbiota are largely uncorrelated. We also find that the general pattern of similarity between host phylogeny and microbiota similarity is weak. Together, we see that bird microbiota are not strongly tied to host size or evolutionary history.

Independent and sensory human mitochondrial functions reflecting symbiotic evolution

The bacterial origin of mitochondria has been a widely accepted as an event that occurred about 1.45 billion years ago and endowed cells with internal energy producing organelle. Thus, mitochondria have traditionally been viewed as subcellular organelle as any other - fully functionally dependent on the cell it is a part of. However, recent studies have given us evidence that mitochondria are more functionally independent than other organelles, as they can function outside the cells, engage in complex "social" interactions, and communicate with each other as well as other cellular components, bacteria and viruses. Furthermore, mitochondria move, assemble and organize upon sensing different environmental cues, using a process akin to bacterial quorum sensing. Therefore, taking all these lines of evidence into account we hypothesize that mitochondria need to be viewed and studied from a perspective of a more functionally independent entity. This view of mitochondria may lead to new insights into their biological function, and inform new strategies for treatment of disease associated with mitochondrial dysfunction.

The role of microbiome-host interactions in the development of Alzheimer´s disease

Alzheimer`s disease (AD) is the most prevalent cause of dementia. It is often assumed that AD is caused by an aggregation of extracellular beta-amyloid and intracellular tau-protein, supported by a recent study showing reduced brain amyloid levels and reduced cognitive decline under treatment with a beta-amyloid-binding antibody. Confirmation of the importance of amyloid as a therapeutic target notwithstanding, the underlying causes of beta-amyloid aggregation in the human brain, however, remain to be elucidated. Multiple lines of evidence point towards an important role of infectious agents and/or inflammatory conditions in the etiology of AD. Various microorganisms have been detected in the cerebrospinal fluid and brains of AD-patients and have thus been hypothesized to be linked to the development of AD, including Porphyromonas gingivalis (PG) and Spirochaetes. Intriguingly, these microorganisms are also found in the oral cavity under normal physiological conditions, which is often affected by multiple pathologies like caries or tooth loss in AD patients. Oral cavity pathologies are mostly accompanied by a compositional shift in the community of oral microbiota, mainly affecting commensal microorganisms and referred to as 'dysbiosis'. Oral dysbiosis seems to be at least partly mediated by key pathogens such as PG, and it is associated with a pro-inflammatory state that promotes the destruction of connective tissue in the mouth, possibly enabling the translocation of pathogenic microbiota from the oral cavity to the nervous system. It has therefore been hypothesized that dysbiosis of the oral microbiome may contribute to the development of AD. In this review, we discuss the infectious hypothesis of AD in the light of the oral microbiome and microbiome-host interactions, which may contribute to or even cause the development of AD. We discuss technical challenges relating to the detection of microorganisms in relevant body fluids and approaches for avoiding false-positives, and introduce the antibacterial protein lactoferrin as a potential link between the dysbiotic microbiome and the host inflammatory reaction.

Metatranscriptome analysis of blood in healthy individuals and irritable bowel syndrome patients

Introduction. Although the presence of micro-organisms in the blood of healthy humans is a relatively new concept, there is a growing amount of evidence that blood might have its own microbiome.Gap Statement. Previous research has targeted the taxonomic composition of the blood microbiome using DNA-based sequencing methods, while little information is known about the presence of microbial transcripts obtained from the blood and their relation to conditions connected with increased gut permeability.Aim. To detect potentially alive and active micro-organisms and investigate differences in taxonomic composition between healthy people and patients with irritable bowel syndrome (IBS), we used the metatranscriptomics approach.Methodology. We collected blood samples from 23 IBS patients and 26 volunteers from the general population, and performed RNAseq on the isolated RNA. Reads corresponding to microbial genomes were identified with Kraken 2's standard plus protozoa and fungi database, and re-estimated at genus level with Bracken 2.7. We looked for trends in the taxonomic composition, making a comparison between the IBS and control groups, accounting for other different factors.Results. The dominant genera in the blood microbiome were found to be Cutibacterium, Bradyrhizobium, Escherichia, Pseudomonas, Micrococcus, Delftia, Mediterraneibacter, Staphylococcus, Stutzerimonas and Ralstonia. Some of these are typical environmental bacteria and could partially represent contamination. However, analysis of sequences from the negative controls suggested that some genera which are characteristic of the gut microbiome (Mediterraneibacter, Blautia, Collinsella, Klebsiella, Coprococcus, Dysosmobacter, Anaerostipes, Faecalibacterium, Dorea, Simiaoa, Bifidobacterium, Alistipes, Prevotella, Ruminococcus) are less likely to be a result of contamination. Differential analysis of microbes between groups showed that some taxa associated with the gut microbiome (Blautia, Faecalibacterium, Dorea, Bifidobacterium, Clostridium, Christensenella) are more prevalent in IBS patients compared to the general population. No significant correlations with any other factors were identified.Conclusion. Our findings support the existence of the blood microbiome and suggest the gut and possibly the oral microbiome as its origin, while the skin microbiome is a possible but less certain source. The blood microbiome is likely influenced by states of increased gut permeability such as IBS.

Exploring the Complex Relationship Between Microbiota and Systemic Lupus Erythematosus

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by various autoantibodies and multi-organ. Microbiota dysbiosis in the gut, skin, oral, and other surfaces has a significant impact on SLE development. This article summarizes relevant research and provides new microbiome-related strategies for exploring the mechanisms and treating patients with SLE.

RECENT FINDINGS

SLE patients have disruptions in multiple microbiomes, with the gut microbiota (bacteria, viruses, and fungi) and their metabolites being the most thoroughly researched. This dysbiosis can promote SLE progression through mechanisms such as the leaky gut, molecular mimicry, and epigenetic regulation. Notwithstanding study constraints on the relationship between microbiota and SLE, specific interventions targeting the gut microbiota, such as probiotics, dietary management, and fecal microbiota transplantation, have emerged as promising SLE therapeutics.

The Gut-Peritoneum Axis in Peritoneal Dialysis and Peritoneal Fibrosis

Peritoneal fibrosis is an important cause of peritoneal dialysis (PD) discontinuation worldwide and is associated with high morbidity and mortality rate. Although the era of metagenomics has provided new insights into the interactions between the gut microbiota and fibrosis in various organs and tissues, its role in peritoneal fibrosis has rarely been discussed. This review provides a scientific rationale and points out the potential role of gut microbiota in peritoneal fibrosis. In addition, the interaction between the gut, circulatory, and peritoneal microbiota is highlighted, with an emphasis on the relationship to PD outcomes. More research is needed to elucidate the mechanisms underlying the role of gut microbiota in peritoneal fibrosis and potentially unveil new target options for the management of PD technique failure.

Impact of local human microbiota on the allergic diseases: Organ-organ interaction

The homogeneous impact of local dysbiosis on the development of allergic diseases in the same organ has been thoroughly studied. However, much less is known about the heterogeneous influence of dysbiosis within one organ on allergic diseases in other organs. A comprehensive analysis of the current scientific literature revealed that most of the relevant publications focus on only three organs: gut, airways, and skin. Moreover, the interactions appear to be mainly unidirectional, that is, dysbiotic conditions of the gut being associated with allergic diseases of the airways and the skin. Similar to homogeneous interactions, early life appears to be not only a crucial period for the formation of the microbiota in one organ but also for the later development of allergic diseases in other organs. In particular, we were able to identify a number of specific bacterial and fungal species/genera in the intestine that were repeatedly associated in the literature with either increased or decreased allergic diseases of the skin, like atopic dermatitis, or the airways, like allergic rhinitis and asthma. The reported studies indicate that in addition to the composition of the microbiome, also the relative abundance of certain microbial species and the overall diversity are associated with allergic diseases of the corresponding organs. As anticipated for human association studies, the underlying mechanisms of the organ-organ crosstalk could not be clearly resolved yet. Thus, further work, in particular experimental animal studies are required to elucidate the mechanisms linking dysbiotic conditions of one organ to allergic diseases in other organs.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

Recovery of metagenomic data from the Aedes aegypti microbiome using a reproducible snakemake pipeline: MINUUR

Background: Ongoing research of the mosquito microbiome aims to uncover novel strategies to reduce pathogen transmission. Sequencing costs, especially for metagenomics, are however still significant. A resource that is increasingly used to gain insights into host-associated microbiomes is the large amount of publicly available genomic data based on whole organisms like mosquitoes, which includes sequencing reads of the host-associated microbes and provides the opportunity to gain additional value from these initially host-focused sequencing projects. Methods: To analyse non-host reads from existing genomic data, we developed a snakemake workflow called MINUUR (Microbial INsights Using Unmapped Reads). Within MINUUR, reads derived from the host-associated microbiome were extracted and characterised using taxonomic classifications and metagenome assembly followed by binning and quality assessment. We applied this pipeline to five publicly available Aedes aegypti genomic datasets, consisting of 62 samples with a broad range of sequencing depths. Results: We demonstrate that MINUUR recovers previously identified phyla and genera and is able to extract bacterial metagenome assembled genomes (MAGs) associated to the microbiome. Of these MAGS, 42 are high-quality representatives with >90% completeness and <5% contamination. These MAGs improve the genomic representation of the mosquito microbiome and can be used to facilitate genomic investigation of key genes of interest. Furthermore, we show that samples with a high number of KRAKEN2 assigned reads produce more MAGs. Conclusions: Our metagenomics workflow, MINUUR, was applied to a range of Aedes aegypti genomic samples to characterise microbiome-associated reads. We confirm the presence of key mosquito-associated symbionts that have previously been identified in other studies and recovered high-quality bacterial MAGs. In addition, MINUUR and its associated documentation are freely available on GitHub and provide researchers with a convenient workflow to investigate microbiome data included in the sequencing data for any applicable host genome of interest.

Garlic consumption in relation to colorectal cancer risk and to alterations of blood bacterial DNA

PURPOSE

Garlic consumption has been inversely associated to intestinal adenoma (IA) and colorectal cancer (CRC) risk, although evidence is not consistent. Gut microbiota has been implied in CRC pathogenesis and is also influenced by garlic consumption. We analyzed whether dietary garlic influence CRC risk and bacterial DNA in blood.

METHODS

We conducted a case-control study in Italy involving 100 incident CRC cases, 100 IA and 100 healthy controls matched by center, sex and age. We used a validated food frequency questionnaire to assess dietary habits and garlic consumption. Blood bacterial DNA profile was estimated using qPCR and16S rRNA gene profiling. We derived odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) of IA and CRC according to garlic consumption from multiple conditional logistic regression. We used Mann-Whitney and chi-square tests to evaluate taxa differences in abundance and prevalence.

RESULTS

The OR of CRC for medium/high versus low/null garlic consumption was 0.27 (95% CI = 0.11-0.66). Differences in garlic consumption were found for selected blood bacterial taxa. Medium/high garlic consumption was associated to an increase of Corynebacteriales order, Nocardiaceae family and Rhodococcus genus, and to a decrease of Family XI and Finegoldia genus.

CONCLUSIONS

The study adds data on the protective effect of dietary garlic on CRC risk. Moreover, it supports evidence of a translocation of bacterial material to bloodstream and corroborates the hypothesis of a diet-microbiota axis as a mechanism behind the role of garlic in CRC prevention.