Putting everything in its place: using the INSDC compliant Pathogen Data Object Model to better structure genomic data submitted for public health applications.

Fast, efficient public health actions require well-organized and coordinated systems that can supply timely and accurate knowledge. Public databases of pathogen genomic data, such as the International Nucleotide Sequence Database Collaboration (INSDC), have become essential tools for efficient public health decisions. However, these international resources began primarily for academic purposes, rather than for surveillance or interventions. Now, queries need to access not only the whole genomes of multiple pathogens but also make connections using robust contextual metadata to identify issues of public health relevance. Databases that over time developed a patchwork of submission formats and requirements need to be consistently organized and coordinated internationally to allow effective searches.To help resolve these issues, we propose a common pathogen data structure called the Pathogen Data Object Model (DOM) that will formalize the minimum pieces of sequence data and contextual data necessary for general public health uses, while recognizing that submitters will likely withhold a wide range of non-public contextual data. Further, we propose contributors use the Pathogen DOM for all pathogen submissions (bacterial, viral, fungal, and parasites), which will simplify data submissions and provide a consistent and transparent data structure for downstream data analyses. We also highlight how improved submission tools can support the Pathogen DOM, offering users additional easy-to-use methods to ensure this structure is followed.

Field-based detection of bacteria using nanopore sequencing: Method evaluation for biothreat detection in complex samples.

From pathogen detection to genome or plasmid closure, the utility of the Oxford Nanopore Technologies (ONT) MinION for microbiological analysis has been well documented. The MinION's small footprint, portability, and real-time analytic capability situates it well to address challenges in the field of unbiased pathogen detection, as a component of a security investigation. To this end, a multicenter evaluation of the effect of alternative analytical approaches on the outcome of MinION-based sequencing, using a set of well-characterized samples, was explored in a field-based scenario. Three expert scientific response groups evaluated known bacterial DNA extracts as part of an international first responder (Chemical, Biological, Radiological) training exercise. Samples were prepared independently for analysis using the Rapid and/or Rapid PCR sequencing kits as per the best practices of each of the participating groups. Analyses of sequence data were in turn conducted using varied approaches including ONTs What's in my pot (WIMP) architecture and in-house computational pipelines. Microbial community composition and the ability of each approach to detect pathogens was compared. Each group demonstrated the ability to detect all species present in samples, although several organisms were detected at levels much lower than expected with some organisms even falling below 1% abundance. Several 'contaminant' near neighbor species were also detected, at low abundance. Regardless of the sequencing approach chosen, the observed composition of the bacterial communities diverged from the input composition in each of the analyses, although sequencing conducted using the rapid kit produced the least distortion when compared to PCR-based library preparation methods. One of the participating groups generated drastically lower sequencing output than the other groups, likely attributed to the limited computer hard drive capacity, and occasional disruption of the internet connection. These results provide further consideration for conducting unbiased pathogen identification within a field setting using MinION sequencing. However, the benefits of this approach in providing rapid results and unbiased detection must be considered along with the complexity of sample preparation and data analytics, when compared to more traditional methods. When utilized by trained scientific experts, with appropriate computational resources, the MinION sequencing device is a useful tool for field-based pathogen detection in mixed samples.

Use of a taxon-specific reference database for accurate metagenomics-based pathogen detection of Listeria monocytogenes in turkey deli meat and spinach.

BACKGROUND: The reliability of culture-independent pathogen detection in foods using metagenomics is contingent on the quality and composition of the reference database. The inclusion of microbial sequences from a diverse representation of taxonomies in universal reference databases is recommended to maximize classification precision for pathogen detection. However, these sizable databases have high memory requirements that may be out of reach for some users. In this study, we aimed to assess the performance of a foodborne pathogen (FBP)-specific reference database (taxon-specific) relative to a universal reference database (taxon-agnostic). We tested our FBP-specific reference database's performance for detecting Listeria monocytogenes in two complex food matrices-ready-to-eat (RTE) turkey deli meat and prepackaged spinach-using three popular read-based DNA-to-DNA metagenomic classifiers: Centrifuge, Kraken 2 and KrakenUniq. RESULTS: In silico host sequence removal led to substantially fewer false positive (FP) classifications and higher classification precision in RTE turkey deli meat datasets using the FBP-specific reference database. No considerable improvement in classification precision was observed following host filtering for prepackaged spinach datasets and was likely a consequence of a higher microbe-to-host sequence ratio. All datasets classified with Centrifuge using the FBP-specific reference database had the lowest classification precision compared to Kraken 2 or KrakenUniq. When a confidence-scoring threshold was applied, a nearly equivalent precision to the universal reference database was achieved for Kraken 2 and KrakenUniq. Recall was high for both reference databases across all datasets and classifiers. Substantially fewer computational resources were required for metagenomics-based detection of L. monocytogenes using the FBP-specific reference database, especially when combined with Kraken 2. CONCLUSIONS: A universal (taxon-agnostic) reference database is not essential for accurate and reliable metagenomics-based pathogen detection of L. monocytogenes in complex food matrices. Equivalent classification performance can be achieved using a taxon-specific reference database when the appropriate quality control measures, classification software, and analysis parameters are applied. This approach is less computationally demanding and more attainable for the broader scientific and food safety communities.

Systematic evaluation of supervised machine learning for sample origin prediction using metagenomic sequencing data.

BACKGROUND: The advent of metagenomic sequencing provides microbial abundance patterns that can be leveraged for sample origin prediction. Supervised machine learning classification approaches have been reported to predict sample origin accurately when the origin has been previously sampled. Using metagenomic datasets provided by the 2019 CAMDA challenge, we evaluated the influence of variable technical, analytical and machine learning approaches for result interpretation and novel source prediction. RESULTS: Comparison between 16S rRNA amplicon and shotgun sequencing approaches as well as metagenomic analytical tools showed differences in normalized microbial abundance, especially for organisms present at low abundance. Shotgun sequence data analyzed using Kraken2 and Bracken, for taxonomic annotation, had higher detection sensitivity. As classification models are limited to labeling pre-trained origins, we took an alternative approach using Lasso-regularized multivariate regression to predict geographic coordinates for comparison. In both models, the prediction errors were much higher in Leave-1-city-out than in 10-fold cross validation, of which the former realistically forecasted the increased difficulty in accurately predicting samples from new origins. This challenge was further confirmed when applying the model to a set of samples obtained from new origins. Overall, the prediction performance of the regression and classification models, as measured by mean squared error, were comparable on mystery samples. Due to higher prediction error rates for samples from new origins, we provided an additional strategy based on prediction ambiguity to infer whether a sample is from a new origin. Lastly, we report increased prediction error when data from different sequencing protocols were included as training data. CONCLUSIONS: Herein, we highlight the capacity of predicting sample origin accurately with pre-trained origins and the challenge of predicting new origins through both regression and classification models. Overall, this work provides a summary of the impact of sequencing technique, protocol, taxonomic analytical approaches, and machine learning approaches on the use of metagenomics for prediction of sample origin.

Evaluation of Oxford Nanopore's MinION Sequencing Device for Microbial Whole Genome Sequencing Applications.

The MinION sequencer (Oxford Nanopore Technologies) is a paradigm shifting device allowing rapid, real time long read sequencing of nucleic acids. Yet external benchmarking of this technologies' capabilities has not been extensively reported, nor has thorough evaluation of its utility for field-based analysis with sub-optimal sample types been described. The aim of this study was to evaluate the capability of the MinION sequencer for bacterial genomic and metagenomic applications, with specific emphasis placed on the quality, yield, and accuracy of generated sequence data. Two independent laboratories at the National Microbiology Laboratory (Public Health Agency of Canada), sequenced a set of microbes in replicate, using the currently available flowcells, sequencing chemistries, and software available at the time of the experiment. Overall sequencing yield and quality improved through the course of this set of experiments. Sequencing alignment accuracy was high reaching 97% for all 2D experiments, though was slightly lower for 1D sequencing (94%). 1D sequencing provided much longer sequences than 2D. Both sequencing chemistries performed equally well in constructing genomic assemblies. There was evidence of barcode cross-over using both the native and PCR barcoding methods. Despite the sub-optimal nature of samples sequenced in the field, sequences attributable to B. anthracis the target organism used in this scenario, could none-the-less be detected. Together, this report showcases the rapid advancement in this technology and its utility in the context of genomic sequencing of microbial isolates of importance to public health.

Application of whole genome sequence analysis to the study of Mycobacterium tuberculosis in Nunavut, Canada.

Canada has one of the lowest rates of tuberculosis (TB) in the world, however, among certain sub-populations, disease incidence rates approach those observed in sub-Saharan Africa, and other high incidence regions. In this study, we applied mycobacterial interspersed repetitive unit (MIRU) variable number of tandem repeat (VNTR) and whole genome sequencing (WGS) to the analysis of Mycobacterium tuberculosis isolates obtained from Northern communities in the territory of Nunavut. WGS was carried out using the Illumina MiSeq, with identified variants used to infer phylogenetic relationships and annotated to infer functional implications. Additionally, the sequencing data from these isolates were augmented with publically available WGS to evaluate data from the Nunavut outbreak in the broader Canadian context. In this study, isolates could be classified into four major clusters by MIRU-VNTR analysis. These could be further resolved into sub-clusters using WGS. No evidence for antimicrobial resistance, either genetic or phenotypic, was observed in this cohort. Among most subjects with multiple samples, reactivation/incomplete treatment likely contributed to recurrence. However, isolates from two subjects appeared more likely to have occurred via reinfection, based on the large number of genomic single nucleotide variants detected. Finally, although quite distinct from previously reported Canadian MTB strains, isolates obtained from Nunavut clustered most closely with a cohort of samples originating in the Nunavik region of Northern Quebec. This study demonstrates the benefit of using WGS for discriminatory analysis of MTB in Canada, especially in high incidence regions. It further emphasizes the importance of focusing epidemiological intervention efforts on interrupting transmission chains of endemic TB throughout Northern communities, rather than relying on strategies applied in regions where the majority of TB cases result from importation of foreign strains.

Custom database development and biomarker discovery methods for MALDI-TOF mass spectrometry-based identification of high-consequence bacterial pathogens.

A high-quality custom database of MALDI-TOF mass spectral profiles was developed with the goal of improving clinical diagnostic identification of high-consequence bacterial pathogens. A biomarker discovery method is presented for identifying and evaluating MALDI-TOF MS spectra to potentially differentiate biothreat bacteria from less-pathogenic near-neighbour species.

Time-to-Detection of Inducible Macrolide Resistance in Mycobacterium abscessus Subspecies and Its Association with the Erm(41) Sequevar.

Mutations in the erm(41) gene of M.abscessus group organisms are associated with differences in inducible macrolide resistance, with current recommendations being to hold rapidly growing isolates for up to 14 days in order to ensure that resistance which develops more slowly can be detected. This study aimed to determine the ideal incubation time for accurate identification of inducible macrolide resistance as well as to determine if there was an association between the time taken to detect inducible resistance in M.abscessus group organisms and their erm(41) sequevar. We amplified and sequenced the erm(41) genes of a total of 104 M.abscessus group isolates and determined their sequevars. The isolates were tested for phenotypic clarithromycin resistance at days 7, 10, 14 and 21, using Trek Diagnostics Sensititre RAPMYCO microbroth dilution plates. Associations between erm(41) gene sequevars and time to detection of resistance were evaluated using Fisher's exact test in R. The samples included in this study fell into 14 sequevars, with the majority of samples falling into Sequevar02 (16), Sequevar06 (15), Sequevar08 (7) and Sequvar 15 (31), and several isolates that were in small clusters, or unique. The majority (82.7%) of samples exhibiting inducible macrolide resistance were interpreted as resistant by day 7. Two isolates in Sequevar02, which has a T28C mutation that is associated with sensitivity, showed intermediate resistance at day 14, though the majority (13) were sensitive at day 14. The majority of isolates with inducible macrolide resistance fell into Sequevars 06,08 and 15, none of which contain the T28C mutation. These sequevars were analyzed to determine if there was any correlation between sequevar and time to detection of resistance. None was found. Based on these findings, we recommend the addition of a day 7 read to the CLSI guidelines to improve turn-around-times for these isolates. It is also recommended that erm(41) gene sequencing be added to routine phenotypic testing for the resolution of cases with difficult-to-interpret phenotypic results.

Intraepithelial lymphocytosis is a frequent finding in biopsies from ileal pouch-anal anastomoses.

Following restorative proctocolectomy with an ileal pouch-anal anastomosis, the small bowel mucosa undergoes several specific histologic adaptions, which may be unrelated to the underlying disease or symptoms of pouchitis. An increase in intraepithelial lymphocytes (IELs) has not been described as part of this spectrum. Mucosal biopsies of the ileal pouch and afferent limb of 230 patients (mean age: 45.7y [18.3-74.7], gender [female/male]: 117/113) with a functioning ileal pouch-anal anastomosis (mean time since ileostomy closure: 10.8months) and associated clinically annotated outcome data were assessed for IELs/100 enterocytes. Forty-two patients (18.3%) showed an increase in IELs (≥20 IELs/100 enterocytes [range 20-39]), in pouch and/or afferent limb biopsies. Intraepithelial lymphocytosis was more commonly observed in afferent limb compared to pouch biopsies (18.8% vs 8.3%; P = .42) and in familial adenomatous polyposis compared to ulcerative colitis patients (16% vs 8%; P = 0.36), but neither difference reached statistical significance. No cases with increased IELs displayed severe villous blunting. Increased IELs were not significantly associated with age, sex, ethnicity, smoking history, time since ileostomy, use of antibiotics, biologic agents, anti-diarrheal agents or probiotics, C-reactive protein levels or differential white cell count. None of the 42 patients with increased IELs had positive celiac serology (anti-human tissue transglutaminase IgA [ELISA] with corresponding total serum IgA). Intraepithelial lymphocytosis in pouch biopsies may represent a subclinical response to an altered bacterial microenvironment. Pathologists should be aware that intraepithelial lymphocytosis is part of the spectrum of changes in pouch biopsies, and only rarely is due to celiac disease.

Microbiome Heterogeneity Characterizing Intestinal Tissue and Inflammatory Bowel Disease Phenotype.

Inflammatory bowel disease has been associated with differential abundance of numerous organisms when compared to healthy controls (HCs); however, few studies have investigated variability in the microbiome across intestinal locations and how this variability might be related to disease location and phenotype. In this study, we have analyzed the microbiome of a large cohort of individuals recruited at Mount Sinai Hospital in Toronto, Canada. Biopsies were taken from subjects with Crohn's disease, ulcerative colitis, and HC, and also individuals having undergone ileal pouch-anal anastomosis for treatment of ulcerative colitis or familial adenomatous polyposis. Microbial 16S rRNA was sequenced using the Illumina MiSeq platform. We observed a great deal of variability in the microbiome characterizing different sampling locations. Samples from pouch and afferent limb were comparable in microbial composition. When comparing sigmoid and terminal ileum samples, more differences were observed. The greatest number of differentially abundant microbes was observed when comparing either pouch or afferent limb samples to sigmoid or terminal ileum. Despite these differences, we were able to observe modest microbial variability between inflammatory bowel disease phenotypes and HCs, even when controlling for sampling location and additional experimental factors. Most detected associations were observed between HCs and Crohn's disease, with decreases in specific genera in the families Ruminococcaceae and Lachnospiraceae characterizing tissue samples from individuals with Crohn's disease. This study highlights important considerations when analyzing the composition of the microbiome and also provides useful insight into differences in the microbiome characterizing these seemingly related phenotypes.

A Study of the Infant Nasal Microbiome Development over the First Year of Life and in Relation to Their Primary Adult Caregivers Using cpn60 Universal Target (UT) as a Phylogenetic Marker.

Whereas the infant gut microbiome is the subject of intense study, relatively little is known regarding the nares microbiome in newborns and during early life. This study aimed to survey the typical composition and diversity of human anterior nare microflora for developing infants over time, and to explore how these correlate to their primary caregivers. Single nare swabs were collected at five time points over a one-year period for each subject from infant-caregiver pairs. Our study comprised of 50 infants (recruited at 2 weeks, post delivery) and their 50 primary caregivers. Applying the chaperonin-60 (cpn60) universal target (UT) amplicon as our molecular barcoding marker to census survey the microbial communities, we longitudinally surveyed infant nares microbiota at 5 time points over the course of the first year of life. The inter- and intra-subject diversity was catalogued and compared, both longitudinally and relative to their adult primary caregivers. Although within-subject variability over time and inter-subject variability were both observed, the assessment detected only one or two predominant genera for individual infant samples, belonging mainly to phyla Actinobacteria, Firmicutes, and Proteobacteria. Consistent with previously observed microbial population dynamics in other body sites, the diversity of nares microflora increased over the first year of life and infants showed differential operational taxonomic units (OTUs) relative to their matched primary caregiver. The collected evidence also support that both temporal and seasonal changes occur with respect to carriage of potentially pathogenic bacteria (PPBs), which may influence host predisposition to infection. This pilot study surveying paired infant/caregiver nare microbiomes provides novel longitudinal diversity information that is pertinent to better understanding nare microbiome development in infants.

Comparison of Sample Preparation Methods Used for the Next-Generation Sequencing of Mycobacterium tuberculosis.

The advent and widespread application of next-generation sequencing (NGS) technologies to the study of microbial genomes has led to a substantial increase in the number of studies in which whole genome sequencing (WGS) is applied to the analysis of microbial genomic epidemiology. However, microorganisms such as Mycobacterium tuberculosis (MTB) present unique problems for sequencing and downstream analysis based on their unique physiology and the composition of their genomes. In this study, we compare the quality of sequence data generated using the Nextera and TruSeq isolate preparation kits for library construction prior to Illumina sequencing-by-synthesis. Our results confirm that MTB NGS data quality is highly dependent on the purity of the DNA sample submitted for sequencing and its guanine-cytosine content (or GC-content). Our data additionally demonstrate that the choice of library preparation method plays an important role in mitigating downstream sequencing quality issues. Importantly for MTB, the Illumina TruSeq library preparation kit produces more uniform data quality than the Nextera XT method, regardless of the quality of the input DNA. Furthermore, specific genomic sequence motifs are commonly missed by the Nextera XT method, as are regions of especially high GC-content relative to the rest of the MTB genome. As coverage bias is highly undesirable, this study illustrates the importance of appropriate protocol selection when performing NGS studies in order to ensure that sound inferences can be made regarding mycobacterial genomes.

Infliximab to Treat Refractory Inflammation After Pelvic Pouch Surgery for Ulcerative Colitis.

BACKGROUND: Inflammatory pouch complications refractory to first-line therapies remain problematic following ileal pouch-anal anastomosis (IPAA) for ulcerative colitis (UC). We evaluated infliximab efficacy and associations with therapeutic response. METHODS: Data from individuals who underwent colectomy and IPAA for UC (2000-2014) were reviewed. Patients with chronic refractory pouchitis (CP) and Crohn's disease (CD)-like outcomes treated with infliximab were included. Pre-treatment parameters and response at median 8 (initial) and 48 weeks (sustained) were measured. Complete response was defined as symptomatic and endoscopic resolution with modified Pouchitis Disease Activity Index (mPDAI) <5. Partial response included mPDAI improvement >2. Serum was analysed for Anti-Saccharomyces cerevisiae antibodies (ASCA), anti-OmpC, anti-CBir1 and perinuclear Anti-Neutrophil Cytoplasmic Antibodies (pANCA). RESULTS: One hundred and fifty-two patients with CP or a CD-like phenotype were identified. Forty-two were treated with infliximab (33% male; age 32.6±2.6 years, 28.5% CD-like). Post-induction response was achieved in 74% (48% complete) and sustained response in 62.6% (29.6% complete). Mean mPDAI and C-reactive protein declined from 8.5±0.3 to 2±3.4 (p < 0.002) and from 29.48±6.2 to 5.76±1.6mg/L (p < 0.001), respectively. Female gender, smoking and presence of anti-CBir1 were associated with infliximab use (p < 0.01) but not response. Pre-treatment mPDAI <10 (p < 0.01), resolution of rectal bleeding (p < 0.001 ) and week 8 endoscopic activity were associated with sustained response (p = 0.04; odds ratio [OR] 2.2; 95% confidence interval [CI] 1.1-16.5]). More than 2 positive antimicrobial antibody titres were associated with non-response (p < 0.05), but did not retain significance in multivariate analysis (p = 0.197; OR 0.632; 95% CI 0.31-1.2). CONCLUSIONS: Infliximab can effectively treat inflammatory pouch complications. Pre-treatment mPDAI <10 and early endoscopy may identify responders.

Associations between host gene expression, the mucosal microbiome, and clinical outcome in the pelvic pouch of patients with inflammatory bowel disease.

BACKGROUND: Pouchitis is common after ileal pouch-anal anastomosis (IPAA) surgery for ulcerative colitis (UC). Similar to inflammatory bowel disease (IBD), both host genetics and the microbiota are implicated in its pathogenesis. We use the IPAA model of IBD to associate mucosal host gene expression with mucosal microbiomes and clinical outcomes. We analyze host transcriptomic data and 16S rRNA gene sequencing data from paired biopsies from IPAA patients with UC and familial adenomatous polyposis. To achieve power for a genome-wide microbiome-transcriptome association study, we use principal component analysis for transcript and clade reduction, and identify significant co-variation between clades and transcripts. RESULTS: Host transcripts co-vary primarily with biopsy location and inflammation, while microbes co-vary primarily with antibiotic use. Transcript-microbe associations are surprisingly modest, but the most strongly microbially-associated host transcript pattern is enriched for complement cascade genes and for the interleukin-12 pathway. Activation of these host processes is inversely correlated with Sutterella, Akkermansia, Bifidobacteria, and Roseburia abundance, and positively correlated with Escherichia abundance. CONCLUSIONS: This study quantifies the effects of inflammation, antibiotic use, and biopsy location upon the microbiome and host transcriptome during pouchitis. Understanding these effects is essential for basic biological insights as well as for well-designed and adequately-powered studies. Additionally, our study provides a method for profiling host-microbe interactions with appropriate statistical power using high-throughput sequencing, and suggests that cross-sectional changes in gut epithelial transcription are not a major component of the host-microbiome regulatory interface during pouchitis.

Microbiome analysis - from technical advances to biological relevance.

The development of culture-independent techniques and next-generation sequencing has led to a staggering rise in the number of microbiome studies over the last decade. Although it remains important to identify the taxa of microbes present in a variety of environmental samples, including the gut microbiomes of healthy and diseased individuals, the next stage of microbiome research will need to focus on uncovering the role of the microbiome rather than its mere composition. Here, we introduce techniques that go beyond identifying the taxa present within a sample and examine the biological function of the microbiome or the host-microbiome interaction.

Analyzing the human microbiome: a "how to" guide for physicians.

The application of high-throughput next-generation sequencing to the analysis of the human microbiome has led to a shift in our understanding of the etiology of complex diseases. In consequence, a great deal of literature can now be found exploring this complex system, and reviewing recent findings. Observations of alterations in the intestinal microbiome associating with inflammatory bowel disease and other chronic conditions are well supported and have been widely accepted by the research community. Yet, it can be difficult to objectively evaluate the importance of these results, given the wide variety of methodologies applied by different groups in the field. The aim of this review is to focus attention on the basic principles involved in microbiome analyses, and to describe factors that may have an impact on the accurate interpretation of results.

Ileal pouch symptoms do not correlate with inflammation of the pouch.

BACKGROUND & AIMS: Pouchitis is the most common complication after ileal pouch-anal anastomosis (IPAA). However, symptoms are not specific. The Pouchitis Disease Activity Index (PDAI) and the Pouchitis Activity Score (PAS) have been used to diagnose pouchitis. We evaluated the correlation between the clinical components of these scores and endoscopic and histologic findings. METHODS: We performed a cross-sectional study, analyzing data from 278 patients from Mount Sinai Hospital (Toronto, Canada) who had an IPAA. Patients underwent pouchoscopy with a biopsy, and data were collected on patients' clinical status. The PDAI and PAS were calculated for each subject. The Spearman rank correlation (ρ) statistical test was used to evaluate correlations between the PDAI scores and PAS, and between total scores and subscores. RESULTS: The total PDAI scores and PAS scores were correlated; the clinical components of each correlated with the total score (ρ = 0.59 and ρ = 0.71, respectively). However, we observed a low level of correlation between clinical and endoscopic or histologic subscores, with ρ of 0.20 and 0.10, respectively, by PDAI, and ρ of 0.19 and 0.04, respectively, by PAS. CONCLUSIONS: There is a low level of correlation between clinical and endoscopic and histologic subscores of patients with IPAA; clinical symptoms therefore might not reflect objective evidence of inflammation. These findings, along with evidence of correlation between total scores and clinical symptoms, indicate that these indices do not accurately identify patients with pouch inflammation. Further research is required to understand additional factors that contribute to clinical symptoms in the absence of objective signs of pouch inflammation.

Complex host genetics influence the microbiome in inflammatory bowel disease.

BACKGROUND: Human genetics and host-associated microbial communities have been associated independently with a wide range of chronic diseases. One of the strongest associations in each case is inflammatory bowel disease (IBD), but disease risk cannot be explained fully by either factor individually. Recent findings point to interactions between host genetics and microbial exposures as important contributors to disease risk in IBD. These include evidence of the partial heritability of the gut microbiota and the conferral of gut mucosal inflammation by microbiome transplant even when the dysbiosis was initially genetically derived. Although there have been several tests for association of individual genetic loci with bacterial taxa, there has been no direct comparison of complex genome-microbiome associations in large cohorts of patients with an immunity-related disease. METHODS: We obtained 16S ribosomal RNA (rRNA) gene sequences from intestinal biopsies as well as host genotype via Immunochip in three independent cohorts totaling 474 individuals. We tested for correlation between relative abundance of bacterial taxa and number of minor alleles at known IBD risk loci, including fine mapping of multiple risk alleles in the Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) gene exon. We identified host polymorphisms whose associations with bacterial taxa were conserved across two or more cohorts, and we tested related genes for enrichment of host functional pathways. RESULTS: We identified and confirmed in two cohorts a significant association between NOD2 risk allele count and increased relative abundance of Enterobacteriaceae, with directionality of the effect conserved in the third cohort. Forty-eight additional IBD-related SNPs have directionality of their associations with bacterial taxa significantly conserved across two or three cohorts, implicating genes enriched for regulation of innate immune response, the JAK-STAT cascade, and other immunity-related pathways. CONCLUSIONS: These results suggest complex interactions between genetically altered host functional pathways and the structure of the microbiome. Our findings demonstrate the ability to uncover novel associations from paired genome-microbiome data, and they suggest a complex link between host genetics and microbial dysbiosis in subjects with IBD across independent cohorts.

Characterization of the gut-associated microbiome in inflammatory pouch complications following ileal pouch-anal anastomosis.

INTRODUCTION: Inflammatory complications following ileal pouch-anal anastomosis (IPAA) for ulcerative colitis (UC) are common and thought to arise through mechanisms similar to de novo onset inflammatory bowel disease. The aim of this study was to determine whether specific organisms in the tissue-associated microbiota are associated with inflammatory pouch complications. METHODS: Patients having previously undergone IPAA were recruited from Mount Sinai Hospital. Clinical and demographic information were collected and a pouchoscopy with biopsy of both the pouch and afferent limb was performed. Patients were classified based on post-surgical phenotype into four outcome groups: familial adenomatous polyposis controls (FAP), no pouchitis, pouchitis, and Crohn's disease-like (CDL). Pyrosequencing of the 16S rRNA V1-V3 hypervariable region, and quantitative PCR for bacteria of interest, were used to identify organisms present in the afferent limb and pouch. Associations with outcomes were evaluated using exact and non-parametric tests of significance. RESULTS: Analysis at the phylum level indicated that Bacteroidetes were detected significantly less frequently (P<0.0001) in the inflammatory outcome groups (pouchitis and CDL) compared to both FAP and no pouchitis. Conversely, Proteobacteria were detected more frequently in the inflammatory groups (P=0.01). At the genus level, organisms associated with outcome were detected less frequently among the inflammatory groups compared to those without inflammation. Several of these organisms, including Bacteroides (P<0.0001), Parabacteroides (P≤2.2x10(-3)), Blautia (P≤3.0x10(-3)) and Sutterella (P≤2.5x10(-3)), were associated with outcome in both the pouch and afferent limb. These associations remained significant even following adjustment for antibiotic use, smoking, country of birth and gender. Individuals with quiescent disease receiving antibiotic therapy displayed similar reductions in these organisms as those with active pouch inflammation. CONCLUSIONS: Specific genera are associated with inflammation of the ileal pouch, with a reduction of typically ubiquitous organisms characterizing the inflammatory phenotypes.

The NOD2insC polymorphism is associated with worse outcome following ileal pouch-anal anastomosis for ulcerative colitis.

BACKGROUND: Inflammatory complications after ileal pouch-anal anastomosis (IPAA) for ulcerative colitis (UC) are common. OBJECTIVE: To investigate whether genetic factors are associated with adverse pouch outcomes such as chronic pouchitis (CP) and a Crohn's disease-like (CDL) phenotype. DESIGN: 866 patients were recruited from three centres in North America: Mount Sinai Hospital (Toronto, Ontario, Canada), the Cleveland Clinic (Cleveland, Ohio, USA) and Penn State Milton S Hershey Medical Center (Hershey, Pennsylvania, USA). DNA and clinical and demographic information were collected. Subjects were classified into post-surgical outcome groups: no chronic pouchitis (NCP), CP and CDL phenotype. RESULTS: Clinical and genetic data were available on 714 individuals. 487 (68.2%) were classified as NCP, 118 (16.5%) CP and 109 (15.3%) CDL. The presence of arthritis or arthropathy (p=0.02), primary sclerosing cholangitis (p=0.009) and duration of time from ileostomy closure to recruitment (p=0.001) were significantly associated with outcome. The NOD2insC (rs2066847) risk variant was the single nucleotide polymorphism (SNP) most significantly associated with pouch outcome (p=7.4×10(-5)). Specifically, it was associated with both CP and CDL in comparison with NCP (OR=3.2 and 4.3, respectively). Additionally, SNPs in NOX3 (rs6557421, rs12661812), DAGLB (rs836518) and NCF4 (rs8137602) were shown to be associated with pouch outcome with slightly weaker effects. A multivariable risk model combining previously identified clinical (smoking status, family history of inflammatory bowel disease), serological (anti-Saccharomyces cerevisiae antibody IgG, perinuclear antineutrophil cytoplasmic antibody and anti-CBir1) and genetic markers was constructed and resulted in an OR of 2.72 (p=8.89×10(-7)) for NCP versus CP/CDL and 3.22 (p=4.11×10(-8)) for NCP versus CDL, respectively. CONCLUSION: Genetic polymorphisms, in particular, the NOD2insC risk allele, are associated with chronic inflammatory pouch outcomes among patients with UC and IPAA.