Project description:The study of antimicrobial resistance (AMR) in infectious diarrhea has generally been limited to cultivation, antimicrobial susceptibility testing and targeted PCR assays. When individual strains of significance are identified, whole genome shotgun (WGS) sequencing of important clones and clades is performed. Genes that encode resistance to antibiotics have been detected in environmental, insect, human and animal metagenomes and are known as "resistomes". While metagenomic datasets have been mined to characterize the healthy human gut resistome in the Human Microbiome Project and MetaHIT and in a Yanomani Amerindian cohort, directed metagenomic sequencing has not been used to examine the epidemiology of AMR. Especially in developing countries where sanitation is poor, diarrhea and enteric pathogens likely serve to disseminate antibiotic resistance elements of clinical significance. Unregulated use of antibiotics further exacerbates the problem by selection for acquisition of resistance. This is exemplified by recent reports of multiple antibiotic resistance in Shigella strains in India, in Escherichia coli in India and Pakistan, and in nontyphoidal Salmonella (NTS) in South-East Asia. We propose to use deep metagenomic sequencing and genome level assembly to study the epidemiology of AMR in stools of children suffering from diarrhea. Here the epidemiology component will be surveillance and analysis of the microbial composition (to the bacterial species/strain level where possible) and its constituent antimicrobial resistance genetic elements (such as plasmids, integrons, transposons and other mobile genetic elements, or MGEs) in samples from a cohort where diarrhea is prevalent and antibiotic exposure is endemic. The goal will be to assess whether consortia of specific mobile antimicrobial resistance elements associate with species/strains and whether their presence is enhanced or amplified in diarrheal microbiomes and in the presence of antibiotic exposure. This work could potentially identify clonal complexes of organisms and MGEs with enhanced resistance and the potential to transfer this resistance to other enteric pathogens. We have performed WGS, metagenomic assembly and gene/protein mapping to examine and characterize the types of AMR genes and transfer elements (transposons, integrons, bacteriophage, plasmids) and their distribution in bacterial species and strains assembled from DNA isolated from diarrheal and non-diarrheal stools. The samples were acquired from a cohort of pediatric patients and controls from Colombia, South America where antibiotic use is prevalent. As a control, the distribution and abundance of AMR genes can be compared to published studies where resistome gene lists from healthy cohort sequences were compiled. Our approach is more epidemiologic in nature, as we plan to identify and catalogue antimicrobial elements on MGEs capable of spread through a local population and further we will, where possible, link mobile antimicrobial resistance elements with specific strains within the population.

Project description:BACKGROUND: Metagenomic studies carried out in the past decade have led to an enhanced understanding of the gut microbiome in human health, however, the Indian gut microbiome is not well explored yet. We analysed the gut microbiome of 110 healthy individuals from two distinct locations (North-Central and Southern) in India using multi-omics approaches, including 16S rRNA gene amplicon sequencing, whole genome shotgun metagenomic sequencing, and metabolomic profiling of faecal and serum samples. RESULTS: The gene catalogue established in this study emphasizes the uniqueness of the Indian gut microbiome in comparison to other populations. The gut microbiome of the cohort from North-Central India, which was primarily consuming a plant-based diet, was found to be associated with Prevotella, and also showed an enrichment of Branched Chain Amino Acid (BCAA) and lipopolysaccharide (LPS) biosynthesis pathways. In contrast, the gut microbiome of the cohort from Southern India, which was consuming an omnivorous diet, showed associations with Bacteroides, Ruminococcus and Faecalibacterium, and had an enrichment of Short Chain Fatty Acid (SCFA) biosynthesis pathway and BCAA transporters. This corroborated well with the metabolomics results, which showed higher concentration of BCAAs in the serum metabolome of the North-Central cohort and an association with Prevotella. In contrast, the concentration of BCAAs were found higher in the faecal metabolome of the Southern-India cohort, and showed a positive correlation with the higher abundance of BCAA transporters. CONCLUSIONS: The study reveals the unique composition of Indian gut microbiome, establishes the Indian gut microbial gene catalogue, and compares it with the gut microbiome of other populations. The functional associations revealed using metagenomic and metabolomic approaches provide novel insights on the gut-microbe-metabolic axis, which will be useful for future epidemiological and translational researches.

Project description:Mechanisms through which the microbiome communicates with the systemic immune system remain unclear. We have identified a family of microbiome Bacteroidota-derived lipopeptides – the serine-glycine (S/G) lipids, and specifically L654 – that are TLR2 ligands, access the systemic circulation, and potentially link the microbiome and systemic innate immunity. We have previously postulated that L654 and the S/G lipids regulate systemic innate immunity by entering the systemic circulation and mediating weak TLR2 interactions that maintain “normal” levels of innate immune signaling feedback inhibitors. In proof-of-concept studies, we reported that increasing systemic L654 levels in mice by administering exogenous L654 intravenously significantly diminishes systemic innate immune responses and attenuates murine autoimmunity. In the present study, our goal was to confirm the role of the microbiome in mediating this mode of immunoregulation by decreasing the microbiome-based production of S/G lipids. We now report that decreasing microbiome Bacteroidota in mice using a specific oral antibiotic/rest protocol reduces fecal and plasma S/G lipids levels and significantly enhances systemic innate immune responses. Replenishing systemic levels of S/G lipids after antibiotic treatment through exogenous administration of L654 returns innate immune responses to normal levels, confirming the regulatory role of S/G lipids in this mode of microbiome regulation. Finally, RNAseq analysis of splenic monocytes derived from antibiotic-treated and control mice prior to ex vivo stimulation demonstrates that the antibiotic/rest protocol and the concomitant decrease in microbiome S/G lipids and Bacteroidota has significant downregulatory effects on normal homeostatic pro-inflammatory pathways. These effects are also associated with downregulation of specific proinflammatory pathway inhibitors, which may suggest a potential mechanism underlying the enhancement in ex vivo innate immune stimulated responses of these monocytes. Overall, our results suggest that S/G lipids are microbiome-derived bacterial factors capable of regulating systemic innate immunity and as such are manipulatable targets with therapeutic potential for enhancing or decreasing innate immunity in the context of infectious, malignant, and autoimmune diseases.

Project description:Mechanisms through which the microbiome communicates with the systemic immune system remain unclear. We have identified a family of microbiome Bacteroidota-derived lipopeptides – the serine-glycine (S/G) lipids, and specifically L654 – that are TLR2 ligands, access the systemic circulation, and potentially link the microbiome and systemic innate immunity. We have previously postulated that L654 and the S/G lipids regulate systemic innate immunity by entering the systemic circulation and mediating weak TLR2 interactions that maintain “normal” levels of innate immune signaling feedback inhibitors. In proof-of-concept studies, we reported that increasing systemic L654 levels in mice by administering exogenous L654 intravenously significantly diminishes systemic innate immune responses and attenuates murine autoimmunity. In the present study, our goal was to confirm the role of the microbiome in mediating this mode of immunoregulation by decreasing the microbiome-based production of S/G lipids. We now report that decreasing microbiome Bacteroidota in mice using a specific oral antibiotic/rest protocol reduces fecal and plasma S/G lipids levels and significantly enhances systemic innate immune responses. Replenishing systemic levels of S/G lipids after antibiotic treatment through exogenous administration of L654 returns innate immune responses to normal levels, confirming the regulatory role of S/G lipids in this mode of microbiome regulation. Finally, RNAseq analysis of splenic monocytes derived from antibiotic-treated and control mice with or without exogenous L654 prior to ex vivo stimulation demonstrates that the antibiotic/rest protocol and the concomitant decrease in microbiome S/G lipids and Bacteroidota has significant downregulatory effects on normal homeostatic pro-inflammatory pathways. These effects are also associated with downregulation of specific proinflammatory pathway inhibitors, which may suggest a potential mechanism underlying the enhancement in ex vivo innate immune stimulated responses of these monocytes. Overall, our results suggest that S/G lipids are microbiome-derived bacterial factors capable of regulating systemic innate immunity and as such are manipulatable targets with therapeutic potential for enhancing or decreasing innate immunity in the context of infectious, malignant, and autoimmune diseases.

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