A key step in microbiome sequencing analysis is read assignment to taxonomic units. This is often performed using one of four taxonomic classifications, namely SILVA, RDP, Greengenes or NCBI. It is ...unclear how similar these are and how to compare analysis results that are based on different taxonomies.
We provide a method and software for mapping taxonomic entities from one taxonomy onto another. We use it to compare the four taxonomies and the Open Tree of life Taxonomy (OTT).
While we find that SILVA, RDP and Greengenes map well into NCBI, and all four map well into the OTT, mapping the two larger taxonomies on to the smaller ones is problematic.
The human gut resistome van Schaik, Willem
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
06/2015, Volume:
370, Issue:
1670
Journal Article
Peer reviewed
Open access
In recent decades, the emergence and spread of antibiotic resistance among bacterial pathogens has become a major threat to public health. Bacteria can acquire antibiotic resistance genes by the ...mobilization and transfer of resistance genes from a donor strain. The human gut contains a densely populated microbial ecosystem, termed the gut microbiota, which offers ample opportunities for the horizontal transfer of genetic material, including antibiotic resistance genes. Recent technological advances allow microbiota-wide studies into the diversity and dynamics of the antibiotic resistance genes that are harboured by the gut microbiota (‘the gut resistome’). Genes conferring resistance to antibiotics are ubiquitously present among the gut microbiota of humans and most resistance genes are harboured by strictly anaerobic gut commensals. The horizontal transfer of genetic material, including antibiotic resistance genes, through conjugation and transduction is a frequent event in the gut microbiota, but mostly involves non-pathogenic gut commensals as these dominate the microbiota of healthy individuals. Resistance gene transfer from commensals to gut-dwelling opportunistic pathogens appears to be a relatively rare event but may contribute to the emergence of multi-drug resistant strains, as is illustrated by the vancomycin resistance determinants that are shared by anaerobic gut commensals and the nosocomial pathogen Enterococcus faecium.
Metagenomic next-generation sequencing (mNGS) for pathogen detection is becoming increasingly available as a method to identify pathogens in cases of suspected infection. mNGS analyzes the nucleic ...acid content of patient samples with high-throughput sequencing technologies to detect and characterize microorganism DNA and/or RNA. This unbiased approach to organism detection enables diagnosis of a broad spectrum of infection types and can identify more potential pathogens than any single conventional test. This can lead to improved ability to diagnose patients, although there remains concern regarding contamination and detection of nonclinically significant organisms.
We describe the laboratory approach to mNGS testing and highlight multiple considerations that affect diagnostic performance. We also summarize recent literature investigating the diagnostic performance of mNGS assays for a variety of infection types and recommend further studies to evaluate the improvement in clinical outcomes and cost-effectiveness of mNGS testing.
The majority of studies demonstrate that mNGS has sensitivity similar to specific PCR assays and will identify more potential pathogens than conventional methods. While many of these additional organism detections correlate with the expected pathogen spectrum based on patient presentations, there are relatively few formal studies demonstrating whether these are true-positive infections and benefits to clinical outcomes. Reduced specificity due to contamination and clinically nonsignificant organism detections remains a major concern, emphasizing the importance of careful interpretation of the organism pathogenicity and potential association with the clinical syndrome. Further research is needed to determine the possible improvement in clinical outcomes and cost-effectiveness of mNGS testing.
There is an increasing demand for accurate and fast metagenome classifiers that can not only identify bacteria, but all members of a microbial community. We used a recently developed concept in read ...mapping to develop a highly accurate metagenomic classification pipeline named CCMetagen. The pipeline substantially outperforms other commonly used software in identifying bacteria and fungi and can efficiently use the entire NCBI nucleotide collection as a reference to detect species with incomplete genome data from all biological kingdoms. CCMetagen is user-friendly, and the results can be easily integrated into microbial community analysis software for streamlined and automated microbiome studies.
There are more than 1000 microbial species living in the complex human intestine.The gut microbial community plays an important role in protecting the host against pathogenic microbes,modulating ...immunity,regulating metabolic processes,and is even regarded as an endocrine organ.However,traditional culture methods are very limited for identifying microbes.With the application of molecular biologic technology in the field of the intestinal microbiome,especially metagenomic sequencing of the next-generation sequencing technology,progress has been made in the study of the human intestinal microbiome.Metagenomics can be used to study intestinal microbiome diversity and dysbiosis,as well as its relationship to health and disease.Moreover,functional metagenomics can identify novel functional genes,microbial pathways,antibiotic resistance genes,functional dysbiosis of the intestinal microbiome,and determine interactions and co-evolution between microbiota and host,though there are still some limitations.Metatranscriptomics,metaproteomics and metabolomics represent enormous complements to the understanding of the human gut microbiome.This review aims to demonstrate that metagenomics can be a powerful tool in studying the human gut microbiome with encouraging prospects.The limitations of metagenomics to be overcome are also discussed.Metatranscriptomics,metaproteomics and metabolomics in relation to the study of the human gut microbiome are also briefly discussed.
Abstract
Background
Metagenomic next-generation sequencing (mNGS) of plasma cell-free DNA has emerged as an attractive diagnostic modality allowing broad-range pathogen detection, noninvasive ...sampling, and earlier diagnosis. However, little is known about its real-world clinical impact as used in routine practice.
Methods
We performed a retrospective cohort study of all patients for whom plasma mNGS (Karius test) was performed for all indications at 5 United States institutions over 1.5 years. Comprehensive records review was performed, and standardized assessment of clinical impact of the mNGS based on the treating team’s interpretation of Karius results and patient management was established.
Results
A total of 82 Karius tests were evaluated from 39 (47.6%) adults and 43 (52.4%) children and a total of 53 (64.6%) immunocompromised patients. Karius positivity rate was 50 of 82 (61.0%), with 25 (50.0%) showing 2 or more organisms (range, 2–8). The Karius test results led to positive impact in 6 (7.3%), negative impact in 3 (3.7%), and no impact in 71 (86.6%), and was indeterminate in 2 (2.4%). Cases with positive Karius result and clinical impact involved bacteria and/or fungi but not DNA viruses or parasites. In 10 patients who underwent 16 additional repeated tests, only 1 was associated with clinical impact.
Conclusions
The real-world impact of the Karius test as currently used in routine clinical practice is limited. Further studies are needed to identify high-yield patient populations, define the complementary role of mNGS to conventional microbiological methods, and discern how best to integrate mNGS into current testing algorithms.
In a multicenter retrospective cohort study, we show that the real-world clinical impact of plasma metagenomic next-generation sequencing (mNGS) for the noninvasive diagnosis of infections is limited (positive impact, 7.3%). Further studies are needed to optimize the impact of mNGS.
Long-term complications after COVID-19 are common, but the potential cause for persistent symptoms after viral clearance remains unclear.
To investigate whether gut microbiome composition is linked ...to post-acute COVID-19 syndrome (PACS), defined as at least one persistent symptom 4 weeks after clearance of the SARS-CoV-2 virus.
We conducted a prospective study of 106 patients with a spectrum of COVID-19 severity followed up from admission to 6 months and 68 non-COVID-19 controls. We analysed serial faecal microbiome of 258 samples using shotgun metagenomic sequencing, and correlated the results with persistent symptoms at 6 months.
At 6 months, 76% of patients had PACS and the most common symptoms were fatigue, poor memory and hair loss. Gut microbiota composition at admission was associated with occurrence of PACS. Patients without PACS showed recovered gut microbiome profile at 6 months comparable to that of non-COVID-19 controls. Gut microbiome of patients with PACS were characterised by higher levels of
,
and lower levels of
. Persistent respiratory symptoms were correlated with opportunistic gut pathogens, and neuropsychiatric symptoms and fatigue were correlated with nosocomial gut pathogens, including
and
(all p<0.05). Butyrate-producing bacteria, including
and
showed the largest inverse correlations with PACS at 6 months.
These findings provided observational evidence of compositional alterations of gut microbiome in patients with long-term complications of COVID-19. Further studies should investigate whether microbiota modulation can facilitate timely recovery from post-acute COVID-19 syndrome.
Long-read sequencing technologies have substantially improved the assemblies of many isolate bacterial genomes as compared to fragmented short-read assemblies. However, assembling complex metagenomic ...datasets remains difficult even for state-of-the-art long-read assemblers. Here we present metaFlye, which addresses important long-read metagenomic assembly challenges, such as uneven bacterial composition and intra-species heterogeneity. First, we benchmarked metaFlye using simulated and mock bacterial communities and show that it consistently produces assemblies with better completeness and contiguity than state-of-the-art long-read assemblers. Second, we performed long-read sequencing of the sheep microbiome and applied metaFlye to reconstruct 63 complete or nearly complete bacterial genomes within single contigs. Finally, we show that long-read assembly of human microbiomes enables the discovery of full-length biosynthetic gene clusters that encode biomedically important natural products.
We present two standards developed by the Genomic Standards Consortium (GSC) for reporting bacterial and archaeal genome sequences. Both are extensions of the Minimum Information about Any (x) ...Sequence (MIxS). The standards are the Minimum Information about a Single Amplified Genome (MISAG) and the Minimum Information about a Metagenome-Assembled Genome (MIMAG), including, but not limited to, assembly quality, and estimates of genome completeness and contamination. These standards can be used in combination with other GSC checklists, including the Minimum Information about a Genome Sequence (MIGS), Minimum Information about a Metagenomic Sequence (MIMS), and Minimum Information about a Marker Gene Sequence (MIMARKS). Community-wide adoption of MISAG and MIMAG will facilitate more robust comparative genomic analyses of bacterial and archaeal diversity.
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