A33 EFFECTS OF THE NEXT GENERATION PROBIOTIC, AKKERMANSIA MUCINIPHILA, ON INTESTINAL INFLAMMATION AND BARRIER FUNCTION

Background

Inflammatory bowel disease (IBD), characterised by chronic intestinal inflammation, is hypothesised to arise from the interplay between susceptibility genes, the immune system, environmental factors, and gut microbiota. Akkermansia muciniphila is a symbiotic bacterium that accounts for 1-5% of the human fecal microbiota. This microbe has been hailed as a next-generation probiotic, principally with regard to its plethora of beneficial host interactions, including the ability to influence mucin secretion and strengthen the intestinal barrier.

Purpose

Though a clear-cut role and mechanism by which A. muciniphila influences inflammatory conditions is unknown, evidence indicates this microbe is depleted in IBD, suggesting it may have protective effects that are lost in these conditions. Here, we investigate the role and mechanism of A. muciniphila in intestinal inflammation and its influence on intestinal barrier function by utilizing barrier-disrupting models of colitis.

Method

Across several experimental models of intestinal inflammation including the chemically-induced dextran sulphate sodium (DSS) model, the parasitic-based model of Trichuris muris infection, and the spontaneous Muc2-/- model, A.muciniphila was administered by oral gavage. Disease activity index, macroscopic scoring and histological scoring were all performed to assess the severity of intestinal inflammation. Various pro- and anti-inflammatory cytokines were assessed within colonic tissue using commercially available ELISA kits.To investigate the effects that A. muciniphila has on barrier function in the context of colitis, reverse transcriptase qPCR was used to explore several factors, including several TJPs, AMPs, and mucins. To analyse the composition of the microbiota and changes in diversity with A. muciniphila supplementation, 16S rRNA sequencing of fecal samples was performed.

Result(s)

Though only minor benefits were derived from this microbe in germ-free mice, in specific pathogen-free (SPF) mice, administration of pasteurized A. muciniphila in a DSS recovery model ameliorated inflammation severity and promoted recovery compared to controls. When gavaged prior to DSS administration, both live and pasteurized A. muciniphila failed to diminish inflammatory markers indicating minimal preventative effects. T. muris-infected SPF mice treated with live A. muciniphila showed increased levels of Th2 and anti-inflammatory cytokines, decreased worm burden, and enhanced levels of the mucin, Muc5ac, compared with those receiving control broth or pasteurized bacteria. Further, both live and pasteurized A. muciniphila ameliorated the severity of inflammation in a mucin 2 deficient (Muc2^-/-) mouse model of spontaneous colitis, indicating that these protective effects are Muc2-independent.

Conclusion(s)

These observations provide us not only with an enhanced understanding of the role A. muciniphila plays in the pathogenesis of intestinal inflammatory conditions but also may fuel novel avenues of treatment for those with IBD.

Please acknowledge all funding agencies by checking the applicable boxes below

CIHR

Disclosure of Interest

None Declared

A8 MICROBIAL ACTIVATION OF INTESTINAL DENDRITIC CELLS IS CRITICAL FOR THE ESTABLISHMENT OF NORMAL BEHAVIOR

Background

Accumulating evidence suggests that gut microbiota affects brain development and its function. It is well known that compared with conventional mice (SPF), germ-free (GF) mice display higher exploratory behavior, which normalizes after bacterial colonization. However, little is known about the underlying mechanisms and first critical steps initiating microbiota-gut-brain communication, which lead to establishment of normal behavior.

Purpose

To investigate the role of immune system in the establishment of normal behavior after bacterial colonization.

Method

We assessed behavior in GF mice before and after colonization with SPF microbiota, Altered Schaedler Flora (ASF) or the single bacterial strain E. coli JM83, and compared them to SPF mice, using the light-dark preference and tail suspension tests. Levels of brain-derived neurotrophic factor (BDNF) and c-Fos expression were measured by immunofluorescence in the hippocampus and amygdala. Colonic and brain gene expression were assessed using a NanoString technology. The immunodeficient MyD88-/- Ticam1- and SCID mice were used to study the role of the innate and adaptive immune systems. To demonstrate the role of the dendritic cells (DCs), we measured behavior before and after mono-colonization with E. coli JM83 in GF mice treated with cosalane and fingolimod, that inhibit DCs activation and migration, respectively. Brain levels of CD11b, CD11c and CD103 as DCs markers was assessed by immunofluorescence.

Result(s)

Compared to SPF mice, GF mice showed higher exploratory and less depressive-like behavior. The ex-germ-free mice colonized with ASF microbiota, or mono-colonized with E. coli JM83 showed similar normalization of behavior as those colonized with SPF microbiota. Mono-colonization with E. coli reduced both BDNF and c-fos levels in the hippocampus and amygdala. While colonization of GF SCID mice induced same change in behavior as in wild-type mice, GF MyD88-/-Ticam1-/- mice did not alter their behavior. Mono-colonization affected multiple genes in the colon and the brain, associated with innate immunity and neural plasticity. Treatment with both cosalane and fingolimod prevented behavioral changes after colonization, which was paralleled by absence of CD11b+CD103+CD11c+ cells in the brain, otherwise found in high numbers in control mono-colonized mice and absent in germ-free mice.

Conclusion(s)

The innate immune system, through activation and migration of intestinal dendritic cells into the brain, initiates the neuro-immune signaling within the gut-brain axis and leads to normalization of behavior after bacterial colonization. Our findings may impact several psychiatric conditions, in which altered innate immune signaling has been implicated.

Please acknowledge all funding agencies by checking the applicable boxes below

CIHR, Other

Please indicate your source of funding;

Balsam Family Foundation

Disclosure of Interest

None Declared

A45 FIBER-FREE DIET REDUCES BACTEROIDES ABUNDANCE AND PREVENTS MUCUS DEGRADATION IN MICE COLONIZED WITH MICROBIOTA FROM PATIENTS WITH GENERALIZED ANXIETY DISORDER

Background

Generalized anxiety disorder (GAD) is a debilitating condition with a lifetime prevalence of 4-7% worldwide. We have previously found that compared to healthy controls, GAD patients had lower reported fiber intake, increased gastrointestinal symptoms; and enrichment of Bacteroides genus as well as carbohydrate metabolism pathways (as determined by PICRUSt2, correlated to Bacteroides abundance). Bacteroides are known for its ability to degrade a wide variety of host polysaccharides, such as the intestinal mucus, which could lead to local and systemic inflammation. In this regard, GAD patients had higher C-reactive protein (CRP) compared to healthy controls (p=0.049).

Purpose

To investigate whether a fiber-free diet could decrease Bacteroides abundance and prevent damage of the mucus layer reducing anxiety-behavior in mice with GAD microbiota.

Method

Two germ-free NIH Swiss mouse breeding pairs were colonized with GAD microbiota using patients’ stool samples and kept on either fiber-free or 10 % inulin (fiber) diet. Offspring were weaned at week 3 and psychometric tests were performed at 10 weeks of age. After sacrifice, samples for histology (mucus layer thickness determination), blood (CRP ELISA determination) and stool (Illumina 16S rRNA gene sequencing) were collected. The microbiota data was analyzed following the pipelines of dada2 and by mean comparisons, correlation, AncomBC using R software (v.1.2.1335). Multiple comparison results were corrected allowing 5% of FDR.

Result(s)

Beta diversity analysis showed that parent and offspring’s (n=24 fiber-supplemented and n=14 fiber-free groups) microbiota was similar to the GAD donor. The most differentially abundant bacterial taxon was Bacteroides uniformis, which was decreased in the fiber-free group (p.adj= 0.003). Furthermore, fiber-free diet reduced the overall Bacteroides abundance by half compared to the donor and fiber-supplemented mice group. This led to a thickening (p.adj=0.027) of the mucus layer, increasing from 30 µm (fiber-supplemented diet) to 60 µm in the fiber-free diet group. B. uniformis was negatively correlated to the mucus layer thickness (R= -0.81; p.adj=0.26), although not statistically significant, likely due to a low n number (n=4). We only found a statistical trend for higher CRP levels and anxiety-like behavior in the fiber-supplemented group. This might be because fiber supplementation has several beneficial effects that can counteract the proposed increase in anxiety-like behavior fromBacteroides. Despite that, we found a significant correlation between B. uniformis and time mice spent in the dark (indicative of anxiety-like behavior) in the light preference test.

Conclusion(s)

Our data suggests that Bacteroides abundance, specifically Bacteroides uniformis, contributes to the degradation of the mucus layer and potentially triggers low grade gut inflammation and anxiety-like behavior.

Please acknowledge all funding agencies by checking the applicable boxes below

CIHR

Disclosure of Interest

None Declared

A267 IDENTIFYING ENTEROBACTERIACEAE VIRULENCE GENES ASSOCIATED WITH ACTIVE DISEASE IN ULCERATIVE COLITIS PATIENTS USING CULTURE-DEPENDENT AND -INDEPENDENT APPROACHES

Background

The prevalence of inflammatory bowel disease (IBD) in Canada is among the highest in the world and is estimated to affect 1 in 100 Canadians by 2030. Ulcerative colitis (UC) is a type of IBD characterized by mucosal inflammation of the large intestine. UC is believed to arise through a complex interplay of the host immune responses and changes in the gut microbiota in a genetically susceptible individual. Therapies targeting the gut microbiota, such as antibiotics and fecal microbiota transplantation (FMT), have been effective in treating UC, suggesting infectious triggers should be explored.

Purpose

Some data suggests the development of UC can be driven by pathogenic bacteria of the family Enterobacteriaceae, which can carry virulence genes important for colonizing the gut (e.g. fimH) and disrupting the intestinal epithelium (e.g. hylA). However, many studies have focused on a single species (e.g. Escherichia coli) and thereby underestimate the importance of these virulence genes that are shared across the Enterobacteriaceae family. I aim to investigate whether specific virulence genes contribute to disease activity in some patients with UC and to show that these virulence genes are carried by strains of many Enterobacteriaceae species.

Method

UC patient stool samples were collected throughout enrolment in randomized control trials of FMT for adult UC and microbiome studies in early-onset pediatric UC. The stool samples were cultured on MacConkey agar to enrich for Enterobacteriaceae. Samples from before and after treatment were sent for targetted cultured-enriched metagenomic sequencing and strains were isolated from baseline samples only for whole genome sequencing. The taxonomy of each genome and taxonomic composition of each metagenome were annotated along with virulence genes and antimicrobial resistance genes. Phenotypic assays of cultured isolates were used to capture diversity and virulence activity.

Result(s)

Approximately 7500 colonies from UC patient stool samples were isolated and phenotyped. Based on the initial screens, 130 isolates were selected to comprise our Enterobacteriaceae strain collection. Across all patient samples, we detected 19 different species of the Enterobacteriaceae family across six genera from the genomic and metagenomic data. We identified virulence genes found across multiple species from the Enterobacteriaceae family within genomes and metagenomes, and by performing phenotypic assays of the cultured isolates.

Conclusion(s)

Further exploration of the distribution of these virulence genes in UC patients during active disease or remission and healthy controls can provide insight into the pathogenesis of UC. Identifying infectious agents in even a subset of UC patients will allow for more targeted diagnosis and treatment approaches.

Disclosure of Interest

None Declared

Alterations in fecal β-defensin-3 secretion as a marker of instability of the gut microbiota

Compositional changes in the microbiota (dysbiosis) may be a basis for Irritable Bowel Syndrome (IBS), but biomarkers are currently unavailable to direct microbiota-directed therapy. We therefore examined whether changes in fecal β-defensin could be a marker of dysbiosis in a murine model. Experimental dysbiosis was induced using four interventions relevant to IBS: a mix of antimicrobials, westernized diets (high-fat/high-sugar and high salt diets), or mild restraint stress. Fecal mouse β-defensin-3 and 16S rRNA-based microbiome profiles were assessed at baseline and during and following these interventions. Each intervention, except for mild restraint stress, altered compositional and diversity profiles of the microbiota. Exposure to antimicrobials or a high-fat/high-sugar diet, but not mild restraint stress, resulted in decreased fecal β-defensin-3 compared to baseline. In contrast, exposure to the high salt diet increased β-defensin-3 compared to baseline. Mice exposed to the mix of antimicrobials showed the largest compositional changes and the most significant correlations between β-defensin-3 levels and bacterial diversity. The high salt diet was also associated with significant correlations between changes in β-defensin-3 and bacterial diversity, and this was not accompanied by discernible inflammatory changes in the host. Thus, dietary change or antimicrobial exposure, both recognized factors in IBS exacerbations, induced marked dysbiosis that was accompanied by changes in fecal β-defensin-3 levels. We propose that serial monitoring of fecal β-defensins may serve as a marker of dysbiosis and help identify those IBS patients who may benefit from microbiota-directed therapeutic interventions.

511. The cefazolin (CZ) and piperacillin-tazobactam (TZP) inoculum effects (IEs) are persistent amongst serial isolates of methicillin-sensitive Staphylococcus aureus (MSSA) derived from the sputum of persons with cystic fibrosis (pwCF) despite variation in other phenotypes

Background

Phenotypic diversity among chronically infecting pathogens within the airways of pwCF is increasingly recognized, limiting susceptibility testing-directed decision-making (Somayaji, 2019, JCF). While it is an important outcome determinant in infection (Miller, 2018, OFID), the IE has generally only been studied in acute infection models. Herein, we sought to establish if variation in the presence of the IE to beta-lactams exists among CF-derived MSSA.

Methods

Single sputum cultures from 10 pwCF with chronic MSSA infection of ≥ 10 years in duration were collected, and 10 unique colonies from each were selected and confirmed as MSSA for a total of 100 isolates. Individual isolates were subjected to susceptibility testing at standard (SI: 105 CFU/mL) and high inoculum (HI: 107 CFU/mL) against CZ and TZP and assessed for protease (PRO) and hyaluronidase (HA) production in triplicate. The presence of the IE was defined if a ≥ 4-fold difference in MIC between SI and HI existed. All 100 strains were typed using pulsed-field gel electrophoresis.

Results

Patients included had a median age of 30.5 years, forced vital capacity of 93%, forced expiratory volume in one second of 66% predicted, and a BMI of 21.5 kg/m2. Median sputum MSSA burden was 106 CFU/ml. The IE was overall more common with TZP than CZ: 47% vs 33%, respectively. Median MIC50 for CZ increased between SI and HI: 0.5 to 1µg/mL, and TZP: 2 to 4µg/mL (p< 0.0001 for both). The most prevalent pulsotypes identified corresponded to multilocus sequence types (ST)-5 (20%), ST-30 (15%), and ST-1 (5%), where ST-30 isolates were more likely to exhibit the CZ and TZP IE (p< 0.0001 for both). Eight out of 10 patients had all isolates belonging to the same pulsogroup. Of patients infected with a single strain, discordance between IE phenotype was not noted, though PRO and HA production varied. Among these patients, the standard deviation of zone clearance diameter ranged from 0-0.9cm (mean range: 0-1.4cm) and 0-1.8cm (mean range: 0-7.2cm), respectively, between individual isolates.

Conclusion

Phenotypic diversity in chronic MSSA exists within the airways of pwCF. However, we observed the IE for CZ and TZP to be strain dependent, without variable penetrance.

Disclosures

All Authors: No reported disclosures.

A46 BIOGEOGRAPHIC VARIATION AND FUNCTIONAL PATHWAYS OF THE GUT MICROBIOTA IN CELIAC DISEASE

Background

Genes and gluten are necessary, but insufficient to cause celiac disease (CeD), as risk alleles (DQ2 or DQ8) are prevalent in ~30–40% of the healthy population consuming gluten. Gut microbiota shifts and infections have been proposed as risk modulators. Biogeographic characterization of the microbiota in CeD patients and its functional significance are limited, particularly at the duodenum, the main site of inflammation.

Aims

We studied microbiota composition and predicted function along the gastrointestinal tract and investigated the impact of host genetics and CeD activity.

Methods

We used 16S rRNA gene sequencing (Illumina) and predicted gene function analysis (PICRUSt2), to study the microbiota in duodenal biopsies (D1, D2 and D3), duodenal aspirates, and fecal samples from patients with active CeD (n= 24) (biopsy and serology confirmed) and controls (non-celiac, n= 41). CeD alleles were determined in consented participants using DQ-CD typing. Small intestinal samples from controls (DQ2^-/- = 14; DQ2^+/- = 7) and CeD (DQ2^+/- = 12) were used for further analysis and to colonize C57BL/6 germ-free mice for gluten metabolism studies.

Results

Microbiota community composition and predicted function was mainly determined by intestinal location (P= 0.001). Within the duodenum, but not in stool, CeD patients had increased abundance of opportunistic pathogens. Escherichia coli was increased in D1, Streptococcus pneumoniae in D2, and Neisseria in D3 versus controls. Predicted bacterial protease and peptidase genes were altered in CeD DQ2^+/- patients versus DQ2^-/- controls. In DQ2^+/- controls, fewer predicted bacterial genes were altered compared to CeD DQ2^+/- patients. Impaired capacity to metabolize gluten was confirmed in germ-free mice colonized with microbiota from CeD (DQ2^+/-), but not DQ2^+/- or DQ2^-/- controls.

Conclusions

In the duodenum, CeD is associated with increased opportunistic pathogens and altered bacterial proteolytic profile. These are not determined by genetic predisposition, as CeD and controls with similar genetic background differed in its predicted bacterial proteolytic function, which was confirmed in mice colonized with duodenal microbiota using these cohorts. Our study highlights the need for defining sampling location in studies investigating the role of microbiota in CeD.

Funding Agencies

CAG, CCC, CIHR

A229 GUT MICROBIOTA PROFILES, DIET AND SHORT-CHAIN FATTY ACIDS AS PREDICTORS OF GENERALIZED ANXIETY DISORDER

Background

Generalized anxiety disorder (GAD) is a debilitating chronic condition with a lifetime prevalence of 4–7% worldwide. Both diet and gut microbiota have been previously associated with anxiety.

Aims

To investigate whether bacterial taxa and/or nutrients associate with GAD, and whether they differ from those of healthy controls (HC).

Methods

Patients with GAD (n=82) and matched HC (n=97) were assessed by validated questionnaires for anxiety (DASS-21), gastrointestinal (GI) symptoms (Rome III, Short-Form Leeds Dyspepsia), and dietary profiles by the Dietary Questionnaire for Epidemiological Studies. We quantified several blood and stool biomarkers, including inflammatory and neuroactive metabolites, as well as short-chain fatty acids. Stool microbiota profiles were assessed by16S rRNA gene sequencing through Illumina. The data was then analyzed following the pipelines of dada2 and by multiple factor analysis (MFA), mean comparisons, correlation, LEfSe and XGBoost using R software (v.1.2.1335). Multiple comparison results were corrected allowing 5% of FDR.

Results

Using MFA to analyze all variables, we identified 3 clusters: one mainly composed of HC (n=99, 91% HC, GI symptoms in 25% of subjects), a second mixed cluster (n=30, 80% GAD, GI symptoms in 80%) and a third cluster mainly composed of GAD patients (n=50, 98% GAD, GI symptoms in 86%). When focusing only on the HCs of cluster 1 (n=90) and GADs of cluster 3 (n=49), we found higher GI symptoms, body mass index, serum C-reactive protein and stool calprotectin levels (adj. p=1.3x10-9, 0.001, 0.017 and 0.017, respectively) and lower concentrations of propionate, butyrate and acetate in GAD compared to HC. GADs also reported overall lower caloric intake (kJ/day; adj. p=1.7x10-4) in the food frequency questionnaire. Fibre (g/day) was the macronutrient most negatively associated with anxiety scores (R=-0.44; adj. p=4.2x10-5). Bacteroides was the only bacterial taxon significantly associated with GAD, as well as with anxiety scores (R=0.31, adj. p=0.003). Interestingly, Bacteroides/fiber ratio was strongly correlated to anxiety scores (R=0.58, adj. p=2.7x10-09). Furthermore, demographic, biomarkers and bacterial taxa data were predictive of the patients’ disease state with 92.8% accuracy. The features that aid the model to predict disease state were Bacteroides/fiber ratio, GI symptoms and stool acetate levels.

Conclusions

Our results suggest that most GAD patients differ in dietary and microbiota profiles from HCs, and that the Bacteroides/fiber ratio, stool acetate and GI symptoms might be good predictors of disease state. Furthermore, these data strongly support the role of microbiota-gut-brain axis in genesis of psychiatric diseases, and they will inform mechanistic studies in gnotobiotic mouse models.

Funding Agencies

NIH

A6 MECHANISMS UNDERLYING GUT DYSFUNCTION FOLLOWING C. DIFFICILE INFECTION AND IMPLICATIONS FOR TREATMENT

Background

Recent evidence suggests an increasing prevalence of gut dysfunction following C. difficile infection (CDI). The accompanying prolonged antibiotic (AB) exposure likely contributes to chronic gut dysfunction and our ability to induce gut dysfunction in germ free (GF) mice colonized with microbiota from a patient with severe slow transit post CDI (PCDI) supports this notion (10.1093/jcag/gwz047.117). Furthermore, we were able to restore gut function following fecal microbial transfer from healthy murine donors. Our studies have implicated a role for macrophages in the destruction of the Interstitial Cell of Cajal (ICC) network underlying slow colonic transit in the humanized mouse model. These findings prompted us to evaluate microbiota-directed therapy in normalising gut function in this model.

Aims

1)To investigate whether dietary psyllium rescues the development of slow colonic transit (SCT) through modulating host function via microbiota mediated immune mechanisms; and 2)To evaluate the mechanisms underlying the beneficial effects of psyllium

Methods

GF mice were colonized with either microbiota from the PCDI patient or healthy control (HC) for 3 weeks following which PCDI mice were treated with either a control diet or a 15% psyllium diet (PSY). Colonic motility was assessed before and after the diet intervention using the bead expulsion test. Stool samples were collected for microbial profiling, and short and branched-chain fatty acids (SCFA/BCFA) analysis. Colonic muscle layers encompassing myenteric plexus (MP) were collected for gene expression analysis and to evaluate activated macrophages and ICC degeneration using immunohistochemistry.

Results

Microbiota from a PCDI patient induced a SCT phenotype in GF mice (n=13) as compared to mice colonized with HC microbiota (p=0.0002). Psyllium rescued this SCT phenotype in mice (PCDI(n=7) vs.PSY(n=6):p=0.0014). The psyllium-induced rescue was accompanied by normalization of the ICC network and morphological alterations in infiltrating macrophages. This was supported by changes in immune-related gene expression in the MP including CD11b, NOS, Myd88, Mapk1 and NF-κB. Additionally, bacterial composition was different between PCDI and PSY group (p=0.003). SCFAs like acetic and propionic acid were increased, while BCFA like isobutyric and isovaleric acid were decreased following PSY treatment. These alterations in SCFA/BCFA were supported by fluctuations in specific bacteria like Butyricimonas, Phascolarctobacterium and Allistipes.

Conclusions

Our results provide evidence that chronic gut dysfunction following CDI and AB exposure is microbiota-driven. Furthermore, microbiota-directed therapy using psyllium could serve as a novel therapeutic strategy to normalize gut function via microbiota-mediated restoration of immune homeostasis in these patients.

Funding Agencies

W. Garfield Weston Foundation

Iron in airway macrophages and infective exacerbations of chronic obstructive pulmonary disease

Background

Excess pulmonary iron has been implicated in the pathogenesis of lung disease, including asthma and COPD. An association between higher iron content in sputum macrophages and infective exacerbations of COPD has previously been demonstrated.

Objectives

To assess the mechanisms of pulmonary macrophage iron sequestration, test the effect of macrophage iron-loading on cellular immune function, and prospectively determine if sputum hemosiderin index can predict infectious exacerbations of COPD.

Methods

Intra- and extracellular iron was measured in cell-line-derived and in freshly isolated sputum macrophages under various experimental conditions including treatment with exogenous IL-6 and hepcidin. Bacterial uptake and killing were compared in the presence or absence of iron-loading. A prospective cohort of COPD patients with defined sputum hemosiderin indices were monitored to determine the annual rate of severe infectious exacerbations.

Results

Gene expression studies suggest that airway macrophages have the requisite apparatus of the hepcidin-ferroportin axis. IL-6 and hepcidin play roles in pulmonary iron sequestration, though IL-6 appears to exert its effect via a hepcidin-independent mechanism. Iron-loaded macrophages had reduced uptake of COPD-relevant organisms and were associated with higher growth rates. Infectious exacerbations were predicted by sputum hemosiderin index (β = 0.035, p = 0.035).

Conclusions

We demonstrate in-vitro and population-level evidence that excess iron in pulmonary macrophages may contribute to recurrent airway infection in COPD. Specifically, IL-6-dependent iron sequestration by sputum macrophages may result in immune cell dysfunction and ultimately lead to increased frequency of infective exacerbation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-01929-7.

Disruption of autophagy by increased 5-HT alters gut microbiota and enhances susceptibility to experimental colitis and Crohn's disease

Autophagy, an essential intracellular recycling process, is linked to the pathogenesis of various diseases including Crohn’s disease (CD). Factors that lead to the development of impaired autophagy during intestinal inflammation remain largely unexplored. Here, we report the impact of the interaction between serotonin [5-hydroxytryptamine;(5-HT)] and autophagy in colitis in mouse and human studies. In mice, increased gut 5-HT inhibited autophagy and led to enhanced colitis susceptibility. Reciprocally, mice with reduced 5-HT exhibited up-regulated autophagy via the mammalian target of rapamycin pathway, which resulted in significantly decreased colitis. Deletion of autophagy gene, Atg7, in an epithelial-specific manner, in concert with reduced 5-HT, promoted the development of a colitogenic microbiota and abolished the protective effects conferred by reduced 5-HT. Notably, in control and patient peripheral blood mononuclear cells, we uncovered that 5-HT treatment inhibited autophagy. Our findings suggest 5-HT as a previously unidentified therapeutic target in intestinal inflammatory disorders such as CD that exhibits dysregulated autophagy.

Effect of Probiotics on Incident Ventilator-Associated Pneumonia in Critically Ill Patients: A Randomized Clinical Trial

IMPORTANCE

Growing interest in microbial dysbiosis during critical illness has raised questions about the therapeutic potential of microbiome modification with probiotics. Prior randomized trials in this population suggest that probiotics reduce infection, particularly ventilator-associated pneumonia (VAP), although probiotic-associated infections have also been reported.

OBJECTIVE

To evaluate the effect of Lactobacillus rhamnosus GG on preventing VAP, additional infections, and other clinically important outcomes in the intensive care unit (ICU).

DESIGN, SETTING, AND PARTICIPANTS

Randomized placebo-controlled trial in 44 ICUs in Canada, the United States, and Saudi Arabia enrolling adults predicted to require mechanical ventilation for at least 72 hours. A total of 2653 patients were enrolled from October 2013 to March 2019 (final follow-up, October 2020).

INTERVENTIONS

Enteral L rhamnosus GG (1 × 1010 colony-forming units) (n = 1321) or placebo (n = 1332) twice daily in the ICU.

MAIN OUTCOMES AND MEASURES

The primary outcome was VAP determined by duplicate blinded central adjudication. Secondary outcomes were other ICU-acquired infections including Clostridioides difficile infection, diarrhea, antimicrobial use, ICU and hospital length of stay, and mortality.

RESULTS

Among 2653 randomized patients (mean age, 59.8 years [SD], 16.5 years), 2650 (99.9%) completed the trial (mean age, 59.8 years [SD], 16.5 years; 1063 women [40.1%.] with a mean Acute Physiology and Chronic Health Evaluation II score of 22.0 (SD, 7.8) and received the study product for a median of 9 days (IQR, 5-15 days). VAP developed among 289 of 1318 patients (21.9%) receiving probiotics vs 284 of 1332 controls (21.3%; hazard ratio [HR], 1.03 (95% CI, 0.87-1.22; P = .73, absolute difference, 0.6%, 95% CI, -2.5% to 3.7%). None of the 20 prespecified secondary outcomes, including other ICU-acquired infections, diarrhea, antimicrobial use, mortality, or length of stay showed a significant difference. Fifteen patients (1.1%) receiving probiotics vs 1 (0.1%) in the control group experienced the adverse event of L rhamnosus in a sterile site or the sole or predominant organism in a nonsterile site (odds ratio, 14.02; 95% CI, 1.79-109.58; P < .001).

CONCLUSIONS AND RELEVANCE

Among critically ill patients requiring mechanical ventilation, administration of the probiotic L rhamnosus GG compared with placebo, resulted in no significant difference in the development of ventilator-associated pneumonia. These findings do not support the use of L rhamnosus GG in critically ill patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02462590.

Changes in the gut microbiome associated with infliximab in patients with bipolar disorder

OBJECTIVES

Available information exists supporting the gut-brain axis, but additional information is needed to explore how the gut microbiome changes when exposed to mood disorder treatments. We sought to explore the effects of a novel treatment for bipolar disorder (BD), infliximab, on the gut microbiome.

METHODS

Participants with a primary diagnosis of BD (n = 15) who participated in a 12-week, randomized placebo-controlled trial evaluating the efficacy of adjunctive infliximab in the treatment of BD were recruited and followed. Stool samples were collected prior to randomization and at 12 weeks. 16S rRNA sequencing was employed in order to analyze the gut microbial community profile.

RESULTS

A total of 17 participants were randomized to infliximab (n = 9; mean [SD] age, 47.6 [10.3] years; 8 female) or to placebo (n = 8; mean [SD] age, 45.9 [10.7] years; 7 female) but two participants from the infliximab group were lost to follow-up post randomization. Across all time points, there were no differences in the diversity on either Shannon or Simpson's Diversity indices. Comparison of Aitchison distances revealed a lack of clustering of the microbiota by time point, but did reveal a small overall effect of treatment that was not significantly different at individual time points. There were also no effects of either time or treatment on differential abundance at either the amplicon sequence variant or genus level.

CONCLUSIONS

These observations indicate that no community-wide changes in the microbiota diversity and profile were detected after the use of infliximab treatment.

A51 ENTERIC PARASITE INFECTION-INDUCED ALTERATION OF THE GUT MICROBIOTA REGULATES INTESTINAL GOBLET CELL BIOLOGY AND MUCIN PRODUCTION VIA TLR2 SIGNALING

Background

Goblet cells (GCs) are the major source of mucin which are the main components of the mucus layer that represents the front line of innate defense in the gastrointestinal (GI) tract. Hyperplasia of GCs and increased mucin production are observed in many enteric nematode infections such as Trichuris muris infection. Increased mucin production contributes to parasite clearance by trapping in mucus and inhibiting motility. The GI tract contains trillions of commensal microbes, and these microbes control mucin production from GCs by activating different signaling cascades. During nematode parasite infection due to the coexistence of parasites and microbiota in close proximity of GCs in gut, it is likely that this nematode-microbiota interaction plays an important role in mucin production. Toll-like receptors (TLRs), components of the innate immune system, sense gut microbiota stimuli. The human GC-like cell line, LS174T, expresses TLR2 mRNA which was enhanced by stimulation with synthetic TLR2 ligands. We hypothesize T. muris-induced altered microbiota modulates GC response and mucin production via TLR2 signaling.

Aims

To elucidate the role of T. muris-induced altered gut microbiota in the regulation of intestinal GC response and mucin production via host TLR2 signaling.

Methods

C57BL/6 mice were infected by gavage with ~300 T. muris eggs and infectivity was confirmed by worm burden. Microbiota was analyzed by 16s rRNA sequencing. Colonic GCs response, mucins and TLR2 expression and cytokines production were assessed in germ-free (GF) mice receiving non-infected and T. muris-infected microbiota (collected on day 36 post-infection to exclude worms). Muc2 and Muc5ac expression were assessed in wild-type (WT) and TLR2 deficient (TLR2-/-) mice transplanted with T. muris-infected microbiota following antibiotic treatment.

Results

We observed a difference in microbial composition between non-infected and T. muris infected mice. Transfer of T. muris-infected microbiota into GF mice significantly increased GC numbers and TLR2 expression as well as up-regulated Muc2 and Muc5ac expression and IL-4, IL-13 production compared to GF mice with non-infected microbiota. Antibiotic-treated TLR2-/- mice after receiving microbiota from T. muris-infected mice showed significantly decreased expression of Muc2 and Muc5ac compared to antibiotic-treated WT mice receiving the same microbiota.

Conclusions

T. muris-induced altered microbiota influences intestinal GC response and mucin production via TLR2. In addition to enhancing our understanding on the interaction of parasite with resident microbiota in host defense, this study provides new information on TLR2 based innate signaling in the regulation of GC biology and mucin production.

Funding Agencies

NSERC

A29 NOVEL FECAL BIOMARKERS THAT PRECEDE CLINICAL DIAGNOSIS OF ULCERATIVE COLITIS

Background

Altered gut microbiota composition and function has been associated with inflammatory bowel diseases (IBD) including ulcerative colitis (UC), but causality and mechanisms remain unknown. Most studies have examined patients with active or treated disease and little is known about microbial compositional or functional changes that occur before disease onset.

Aims

We studied a longitudinal cohort of subjects at risk for IBD to define the fecal microbial composition and function in subjects prior to UC onset (pre-UC) and at diagnosis (post-UC), and in matched at-risk subjects that remained healthy.

Methods

Fecal samples were collected from healthy individuals at-risk for IBD (pre-UC; n=13) and subjects were followed longitudinally until UC diagnosis (post-UC, n=9), at which point another fecal sample was collected. Fecal samples from a cohort of matched at-risk individuals that did not develop UC were used as healthy controls (n=48). We applied 16S rRNA gene sequencing, next generation shotgun sequencing, in vitro proteolytic assays and gnotobiotic colonizations to define the microbial composition and proteolytic function in fecal samples.

Results

The microbiota of post-UC subjects clustered separately from pre-UC and HC subjects, based on bray-curtis and unweighted UniFrac, had reduced alpha-diversity, and had reduced abundance of Aldercreutzia compared to pre-UC and HC. In vitro functional analysis revealed increased fecal proteolytic and elastase activity in pre-UC and post-UC samples compared to HC. Metagenomics identified pathways and gene families related to protein metabolism and proteases/peptides that were significantly different between HC and pre-UC samples, suggesting a bacterial component to the pre-UC proteolytic signature. Elastase activity inversely correlated with the relative abundance of Adlercreutzia, and other potentially beneficial taxa, and directly correlated with Bacteroides vulgatus, a known proteolytic taxon. High elastase activity was confirmed in Bacteroides isolates from fecal samples. Bacterial contribution and functional significance of the proteolytic signature was investigated in germ-free adults and litters born from dams colonized with HC, pre-UC or post-UC microbiota. Mice colonized with pre-UC microbiota at adulthood or neonatally developed higher fecal proteolytic activity and an inflammatory immune tone compared with HC colonized mice.

Conclusions

We have identified increased fecal proteolytic activity that precedes clinical diagnosis of UC and associates with gut microbiota changes. This may constitute a non-invasive biomarker of inflammation to monitor at-risk populations that can be targeted therapeutically with anti-proteases.

Funding Agencies

CAG, CCC, CIHR

A39 CULTURE-ENRICHED METAGENOMICS REVEALED MICROBIAL ENGRAFTMENT FOLLOWING FMT IN PATIENTS WITH ULCERATIVE COLITIS

NOT PUBLISHED AT AUTHOR’S REQUEST

Funding Agencies: CIHRImagine SPOR

335 The Gut-Lung Axis: The Human Perspective

The human gastrointestinal tract is the largest immune organ in the body and consequently influences the overall immune state of all body sites. The gut also harbors the largest proportion of the microbiome. In early life, the maturation of the microbiome and immune system are closely entangled, forming a homeostatic system that imparts individuality and stability to the host microbiome. It is now well established that factors that affect early life gut microbiota modulate susceptibility to chronic inflammatory diseases, including airway diseases such as asthma and allergy. Despite this global influence of the gut on immune response in the lungs, local microbiome-immune interactions also shape the response and susceptibility to disease in the airways. The upper respiratory tract and lung microbiomes also contribute to acute and chronic airway diseases. Modulating the gut-lung axis as well as respiratory tract through microbiome-targeted interventions to promote health and reduce susceptibility to infection and chronic inflammatory disease may represent an effective strategy, particularly in early and late life.

Sputum microbiota in adults with CF associates with response to inhaled tobramycin

BACKGROUND

Inhaled tobramycin powder/solution (TIP/S) use has resulted in improved clinical outcomes in patients with cystic fibrosis (CF) with chronic Pseudomonas aeruginosa. However, TIP/S effect on the CF sputum microbiome has not been explored. We hypothesised that TIP/S has additional 'off-target' effects beyond merely P. aeruginosa and that baseline microbiome prior to initiation of therapy is associated with subsequent patient response.

METHODS

We drew sputum samples from a prospectively collected biobank. Patients were included if they had one sputum sample in the 18 months before and after TIP/S. Bacterial 16S rRNA gene profiling was used to characterise the sputum microbiome.

RESULTS

Forty-one patients met our inclusion criteria and 151 sputum samples were assessed. At baseline, median age was 30.4 years (IQR 24.2-35.2) and forced expiratory volume in 1 (FEV₁) second was 57% predicted (IQR 44-74). Nineteen patients were defined a priori as responders having no net decrease in FEV₁ in the year following TIP/S. No significant changes were observed in key microbiome metrics of alpha (within-sample) or beta (between-sample) diversity for samples collected before and after TIP/S. However, significant beta-diversity (Bray-Curtis) differences were noted at baseline between patients based on response status. Notably, responders were observed to have a higher abundance of Staphylococcus in pretherapy baseline samples.

CONCLUSIONS

Our longitudinal study demonstrates that the sputum microbiome of patients with CF is relatively stable following inhaled tobramycin over many months. Intriguingly, our findings suggest that baseline microbiome may associate with patient response to TIP/S-suggesting the sputum microbiome could be used to personalise therapy.

IMAGINE Network's Mind And Gut Interactions Cohort (MAGIC) Study: a protocol for a prospective observational multicentre cohort study in inflammatory bowel disease and irritable bowel syndrome

INTRODUCTION

Gut microbiome and diet may be important in irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and comorbid psychiatric conditions, but the mechanisms are unclear. We will create a large cohort of patients with IBS, IBD and healthy controls, and follow them over time, collecting dietary and mental health information and biological samples, to assess their gastrointestinal (GI) and psychological symptoms in association with their diet, gut microbiome and metabolome.

METHODS AND ANALYSIS

This 5-year observational prospective cohort study is recruiting 8000 participants from 15 Canadian centres. Persons with IBS who are 13 years of age and older or IBD ≥5 years will be recruited. Healthy controls will be recruited from the general public and from friends or relatives of those with IBD or IBS who do not have GI symptoms. Participants answer surveys and provide blood, urine and stool samples annually. Surveys assess disease activity, quality of life, physical pain, lifestyle factors, psychological status and diet. The main outcomes evaluated will be the association between the diet, inflammatory, genetic, microbiome and metabolomic profiles in those with IBD and IBS compared with healthy controls using multivariate logistic regression. We will also compare these profiles in those with active versus quiescent disease and those with and without psychological comorbidity.

ETHICS AND DISSEMINATION

Approval has been obtained from the institutional review boards of all centres taking part in the study. We will develop evidence-based knowledge translation initiatives for patients, clinicians and policymakers to disseminate results to relevant stakeholders.Trial registration number: NCT03131414.

Muc2 Mucin and Nonmucin Microbiota Confer Distinct Innate Host Defense in Disease Susceptibility and Colonic Injury

BACKGROUND & AIMS

Alterations in intestinal MUC2 mucin and microbial diversity are closely linked with important intestinal pathologies; however, their impact on each other and on intestinal pathogenesis has been vaguely characterized. Therefore, it was of interest in this study to delineate distinct and cooperative function of commensal microbiota and the Muc2 mucus barrier in maintaining intestinal epithelial barrier function.

METHODS

Muc2 mucin deficient (Muc2-/-) and sufficient (Muc2+/+) littermates were used as a model for assessing the role of Muc2. To quantify the role of the microbiota in disease pathogenesis, Muc2+/+ and Muc2-/- littermates were treated with a cocktail of antibiotics that reduced indigenous bacteria, and then fecal transplanted with littermate stool and susceptibility to dextran sulphate sodium (DSS) quantified.

RESULTS

Although, Muc2+/+ and Muc2-/- littermates share similar phyla distribution as evidenced by 16S sequencing they maintain their distinctive gastrointestinal phenotypes. Basally, Muc2-/- showed low-grade colonic inflammation with high populations of inflammatory and tolerogenic immune cells that became comparable to Muc2+/+ littermates following antibiotic treatment. Antibiotics treatment rendered Muc2+/+ but not Muc2-/- littermates highly susceptibility to DSS-induced colitis that was ILC3 dependent. Muc2-/- microbiota was colitogenic to Muc2+/+ as it worsened DSS-induced colitis. Microbiota dependent inflammation was confirmed by bone-marrow chimera studies, as Muc2-/- receiving Muc2+/+ bone marrow showed no difference in their susceptibility toward DSS induced colitis. Muc2-/- microbiota exhibited presence of characteristic OTUs of specific bacterial populations that were transferrable to Muc2+/+ littermates.

CONCLUSIONS

These results highlight a distinct role for Muc2 mucin in maintenance of healthy microbiota critical in shaping innate host defenses to promote intestinal homeostasis.

[Not Available]

Objectives:

Compelling animal data exists examining the impact of the gut microbiome on the brain, but work is required to translate these findings in a clinical population. We sought to do this by exploring the effects of antidepressant medications on the gut microbiota, and establishing a baseline Major Depressive Disorder (MDD) gut phenotype.

Methods:

Participants with a primary diagnosis of MDD (n = 15) who were nonmedicated were recruited and followed over 6 months. Stool samples were collected prior to treatment initiation and 3 and 6 months following treatment. 16S rRNA sequencing was employed in order to analyze the gut microbial community profile. Symptom severity was measured by the Beck Depression Inventory. Alpha diversity metrics revealed no significant difference in the community diversity across any of the time-points.

Results:

Comparison of within-group versus between-group distances revealed a lack of clustering of samples based on time-point, suggesting no significant change in the microbiota across treatment duration. When analyzed based on treatment response, however, patients in the responder group exhibited greater phylogenetic diversity than non-responders (Mann-Whitney U = 5, p = 0.026). At 3-months, 35 Operational Taxonomic Units (OTUs) were significantly different between groups and at 6-months, 42 OTUs were significantly different between responders and non-responders.

Conclusions:

These observations indicate that antidepressant medications alter the gut microbiota of patients with MDD, with disparate effects in responders versus non responders. This supports the concept of a microbiota phenotype associate with treatment response in MDD.

Type 2 diabetes influences bacterial tissue compartmentalisation in human obesity

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

Differences in Gut Microbiota in Patients With vs Without Inflammatory Bowel Diseases: A Systematic Review

BACKGROUND & AIMS

Altering the intestinal microbiota has been proposed as a treatment for inflammatory bowel diseases (IBDs), but there are no established associations between specific microbes and IBD. We performed a systematic review to identify frequent associations.

METHODS

We searched the MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases, through April 2, 2018 for studies that compared intestinal microbiota (from fecal or colonic or ileal tissue samples) among patients (adult or pediatric) with IBD vs healthy individuals (controls). The primary outcome was difference in specific taxa in fecal or intestinal tissue samples from patients with IBD vs controls. We used the Newcastle-Ottawa scale to assess the quality of studies included in the review.

RESULTS

We identified 2631 citations; 48 studies from 45 articles were included in the analysis. Most studies evaluated adults with Crohn's disease or ulcerative colitis. All 3 studies of Christensenellaceae and Coriobacteriaceae and 6 of 11 studies of Faecalibacterium prausnitzii reported a decreased amount of those organisms compared with controls, whereas 2 studies each of Actinomyces, Veillonella, and Escherichia coli revealed an increased amount in patients with Crohn's disease. For patients with ulcerative colitis, Eubacterium rectale and Akkermansia were decreased in all 3 studies, whereas E coli was increased in 4 of 9 studies. The microbiota diversity was either decreased or not different in patients with IBD vs controls. Fewer than 50% of the studies stated comparable sexes and ages of cases and controls.

CONCLUSIONS

In a systematic review, we found evidence for differences in abundances of some bacteria in patients with IBD vs controls, but we cannot make conclusions due to inconsistent results and methods among studies. Further large-scale studies, with better methods of assessing microbe populations, are needed.

A50 TRANSFER OF DEPRESSIVE-LIKE PHENOTYPE TO GNOTOBIOTIC MICE DEPENDS ON MICROBIAL FEATURES SPECIFIC TO INDIVIDUAL PATIENTS

Background

Major depressive disorder (MDD) affects approximately 4.4% of the global population. Despite its high prevalence, little is known about the mechanisms underlying this disorder. Recent studies in both humans and rodents have suggested that the intestinal microbiota may play a role in depression. Altered microbiota composition has been found in a subset of MDD patients. Preclinical studies have suggested that fecal microbiota transplant using pooled MDD patient samples can induce depressive-like behaviour in rodents. We have previously shown that the use of different microbiota donors with irritable bowel syndrome results in the induction of different phenotypes in recipient mice. Thus, we have hypothesized that pooling microbiota samples abrogates features that are unique to individual donors.

Aims

(1) Investigate whether the transfer of individual MDD patient microbiota can induce depressive-like behaviour in germ-free (GF) mice

(2) Identify features of individual MDD patient microbiota that are associated with the depressive-like phenotype

Methods

GF NIH Swiss mice of both sexes (min. n=10 per group, total n=110) were colonized with either fecal microbiota from a single donor, MDD patient (MDD1-4) or matched healthy control (HC1-4), or pooled fecal microbiota from MDD1-4 or HC1-4. Mouse behaviour was assessed, using the open field test, three chamber sociability assay, tail suspension test, and sucrose preference test. Stool samples were collected throughout the experiment for 16S rRNA gene sequencing.

Results

Mice colonized with microbiota from patient MDD1 exhibited depressive-like behaviour, as assessed by the sucrose preference test and sociability assay, when compared to mice colonized with HC1 microbiota. This was not true for mice colonized with individual microbiota from the other three patients (MDD2-4) or with pooled MDD microbiota. Comparative analysis of the 16S data revealed a significant difference in Faith’s Phylogenetic Diversity between MDD1 microbiota and pooled MDD microbiota. Four bacterial species were found to be significantly associated with the depressive-like phenotype in mice: Bacteroides acidifaciens, Bacteroides ovatus, unclassified species of Phascolarctobacterium (Veillonellacae family), and Eggerthella lenta. The relative abundances of these species did not differ significantly between the two pooled groups.

Conclusions

Microbiota from some, but not all, MDD patients can induce a depressive-like phenotype in GF mice. The ability to induce depressive-like behaviour in GF mice is lost when microbiota from multiple patients is pooled. Specific bacterial species may be responsible for the successful transfer of the depressive-like phenotype to mice.

Funding Agencies

NIH

A219 PROTECTIVE EFFECTS OF AKKERMANSIA MUCINIPHILA ON INTESTINAL BARRIER FUNCTION AND INFLAMMATION

Background

Akkermansia muciniphila, an anaerobic gram-negative bacteria, accounts for ~3% of human gut microbiota. Despite its mucolytic nature, A. muciniphila has been shown to stimulate mucin production, enhance anti-inflammatory regulatory T cell proliferation and improve gut barrier integrity. Interestingly, an inverse relationship has been established between A. muciniphila and several disease states including inflammatory bowel disease (IBD) suggesting it may have protective and anti-inflammatory effects. However, the precise role and mechanism of A. muciniphila in the pathogenesis of colitis remains unknown. Thus, we hypothesize that A. muciniphila may induce protective effects on intestinal inflammation by influencing host immune response and epithelial barrier integrity.

Aims

(1) To investigate the protective role of A. muciniphila in intestinal inflammation in a chemically induced model of IBD and (2) to investigate the protective role of A. muciniphila in intestinal inflammation and host defense in a model of enteric parasitic infection.

Methods

Colitis was induced in germ-free C57BL/6 mice with 2.5% dextran sulphate sodium (DSS) after treatment with either C57BL/6 wild-type (WT) cecal contents or WT cecal contents supplemented with A. muciniphila. Colitis severity was assessed by disease activity index (DAI), macroscopic and histological scores, myeloperoxidase (MPO) assay and cytokine expression. In addition, colitis was induced by Trichuris muris, an intestinal nematode, following treatment with A. muciniphila. Post-infection, the severity of intestinal inflammation was assessed by worm burden, goblet cell staining, cytokines analysis, MPO activity and Muc2 expression. Microbial composition was assessed by 16s rRNA gene sequencing.

Results

In preliminary studies, mice treated with A. muciniphila and administered DSS for 5 days yielded a significant decrease in DAI, macroscopic scoring, and MPO values compared with controls. IL-10 was also elevated in mice receiving A. muciniphila. Groups receiving A. muciniphila in the T. muris model trended toward decreased worm burden, IL-4, IL-13, as well as increased levels of IL-10, goblet cell expression, and Muc2 and Muc5ac expression. A significant decrease in MPO activity was also observed in the group receiving the A. muciniphila-supplemented gavage. Microbial analysis indicated that 3 weeks post-gavage Akkermansia levels were significantly elevated in groups receiving the A. muciniphila-supplemented WT cecal contents versus WT alone. This significance was maintained post-T. muris infection.

Conclusions

These findings suggest that A. muciniphila may have a protective role in the context of intestinal inflammation. This research has the potential to fuel the development of novel treatments by utilizing this protective role in IBD.

Funding Agencies

CIHR

A45 INFLAMMATION AND INTESTINAL PERMEABILITY IN PEDIATRIC SHORT BOWEL SYNDROME

Background

Both intestinal dysbiosis and central-line associated blood stream infections (CLABSI) have been well documented in children with short bowel syndrome (SBS). Gastrointestinal microbiota prime and regulate mucosal immunity, therefore we hypothesize children with SBS may have longstanding increased intestinal permeability which could lead to mucosal inflammation and predispose to bacteremia.

Aims

We sought to investigate intestinal permeability as well as both intestinal and systemic activation of the inflammatory cascade in children with SBS.

Methods

Two cohorts of children with SBS were consented; with Group 1 including children with SBS requiring central venous catheter (CVC) for parenteral nutrition, and Group 2 including children with SBS without CVC. SBS groups were compared to three control groups including age and sex-matched children with CVC for hematologic disease (Group 3), children without a CVC (Group 4) and healthy adult controls (Group 5). To evaluate intestinal permeability, we quantified circulating bacterial products LPS and MDP through the binding of their respective receptors, TLR4 and NOD2. To determine colonic inflammation, fecal calprotectin was quantified from a single stool sample. Cytokine profiles included IFN-γ, IL-Iβ, IL-8, IL-10, IL-17, TNFα were quantified by Multiplex Immunoassay while gene expression of transcription factors FoxP3+, RORγT, TLR2, and TLR4, were determined by RNA extraction and quantitative PCR.

Results

22 children were recruited in the study (Group 1 n=6, Group 2 n=6, Group 3 n=5, Group 4 n=5) as well as 10 adult control samples (Group 5). The median age of Group 1 was 67 months with a residual small intestine of 26.5cm (IQR 24.7–40) while those in Group 2 were 51 months with a residual small intestine of 55cm (IQR 31.2–89). Circulating bacterial products of LPS and MDP were not different between SBS groups and control children. Serum analysis of cytokine TNFα was significant (p&lt;0.005) however multiple comparator analysis did not identify within group differences. Other cytokines did not differ between groups. Fecal calprotectin levels were not elevated however statistically lower in Group 1 (median 12.8mg/kg; IQR 9.3- 34.9) compared to in Group 2 (median 96mg/kg, IQR 71.6–188.2;) p &lt;0.01. Relative quantification of RNA expression of FoxP3+, RORγT, TLR2, and TLR4 did not differ between groups.

Conclusions

Despite concern of compromised intestinal epithelial barrier function in children with SBS, this study did not detect differences in circulating bacterial products compared to control children as an assessment of intestinal permeability nor increased systemic inflammation. Further research is required to investigate intestinal epithelial barrier function over time and the mechanism of bacteremia in children with SBS.

Funding Agencies

CAGRegional Medical Associates of Hamilton

A261 MICROBIOTA PROFILES OF PATIENTS WITH MENTAL DISODERS DIFFER FROM THOSE OF HEALTHY CONTROLS

Background

Mental disorders are the leading cause of disabilities worldwide, with depression and anxiety among the most common ones, affecting up to 1/3 of the worldwide population at least once in their lifetime. In both preclinical models and clinical studies, gut microbiota has been associated with altered behavior and anxiety or depression, respectively.

Aims

To investigate 1) whether the microbial profiles of patients with generalized anxiety disorder (GAD) and major depression disorder (MDD) differ from those of healthy controls (HC), and 2) whether specific bacterial taxa associate with GAD or MDD.

Methods

118 patients with primary GAD (n=82, 83.3 % female) or MDD (n=36, 62.9 % female) and 99 matched HC (66.6 % female) were recruited through the Anxiety Treatment and Research Centre. Anxiety, depression and stress levels were assessed by DASS-21 questionnaire. Stool samples were collected anaerobically and analysed for 16S rRNA gene sequencing through Illumina technique. The data was divided in 4 groups: 1) mental health disorder (MHD) combining GAD and MDD, 2) GAD, 3) MDD, and 4) HC. The data was analyzed following the pipelines of dada2 and QIIME2. RandomForest plugin for QIIME2 was used to investigate predictive characteristics of MHD, GAD or MDD microbiota. SPSS software v.23 was used to perform Spearman correlations and logistic regressions between microbial taxa and clinical scores.

Results

The mean anxiety score was 16.2 (severe anxiety) for GAD patients and 9.8 (moderate anxiety) for MDD patients; the mean depression score was 19.2 (moderate depression) for MDD patients and 16.0 (moderate depression) for GAD patients, while healthy controls averaged only 1.5 (normal anxiety) and 1.7 (normal depression) for anxiety and depression, respectively. The microbiota profile of the MHD group was predictive of the patients’ disease state with an 83.3% accuracy. In particular, increased relative abundance of Bacteroides ovatus and Bacteroides spp. and decreased relative abundance of Dialister spp. (Veilonellaceae), Haemophilus parainfluenzae and Bifidobacterium adolescentis, were predictive of MHD. Neither the GAD or MDD group microbiota profiles alone were accurate in the prediction of the patients’ disease state. There was a positive correlation between the relative abundance of Bacteroides spp. and a negative correlation between the relative abundance of Clostridium sensu stricto spp. and Sutterella, and the clinical scores of combined MDH and HC groups.

Conclusions

Our data suggest that patients with mental health disorders have different microbiota profiles compared to healthy controls. We have identified specific bacterial signatures that will inform mechanistic studies in gnotobiotic mouse models to investigate further the role of microbiome in mental disorders.

Funding Agencies

NIH

Fast I(n)dentification of Pathogens in Neonates (FINDPATH-N): protocol for a prospective pilot cohort study of next-generation sequencing for pathogen identification in neonates with suspected sepsis

INTRODUCTION

Sepsis is a major source of morbidity and mortality in neonates; however, identification of the causative pathogens is challenging. Many neonates have negative blood cultures despite clinical evidence of sepsis. Next-generation sequencing (NGS) is a high-throughput, parallel sequencing technique for DNA. Pathogen-targeted enrichment followed by NGS has the potential to be more sensitive and faster than current gold-standard blood culture. In this pilot study, we will test the feasibility and pathogen detection patterns of pathogen-targeted NGS in neonates with suspected sepsis. Additionally, the distribution and diagnostic accuracy of biomarkers cell-free DNA and protein C levels at two time points will be explored.

METHODS AND ANALYSIS

We will conduct a prospective, pilot observational study. Neonates over 1 kg with suspected sepsis from a single tertiary care children's hospital will be recruited for the study. Recruitment will be censored at 200 events or 6 months' duration. Two blood study samples will be taken: the first simultaneous to the blood culture (time=0 hour, for NGS and biomarkers) via an exception to consent (deferred consent) and another 24 hours later after prospective consent (biomarkers only). Neonates will be adjudicated into those with clinical sepsis, culture-proven sepsis and without sepsis based on clinical criteria. Feasibility parameters (eg, recruitment) and NGS process time will be reported.For analysis, NGS results will be described in aggregate, compared with the simultaneous blood culture (sensitivity and specificity) and reviewed via expert panel for plausibility. Pilot data for biomarker distribution and diagnostic accuracy (sensitivity and specificity) for distinguishing between septic and non-septic neonates will be reported.

ETHICS AND DISSEMINATION

Ethics approval has been granted by the Hamilton Integrated Research Ethics Board. We will seek publication of study results in peer-reviewed journals.

Analysis of Genetic Association of Intestinal Permeability in Healthy First-degree Relatives of Patients with Crohn's Disease

Excessive intestinal permeability or intestinal barrier dysfunction as measured by various assays has been observed in various diseases. However, little is known about the factors contributing to altered gut permeability in these diseases. Our objective was to determine the genetic determinants of altered gut permeability as measured by the lactulose mannitol fractional excretion ratio (LacMan ratio) in 1075 healthy first-degree relatives of patients with Crohn's disease (CD). In a targeted analysis of single nucleotide polymorphisms (SNPs) located in genes associated with intestinal barrier function related or not to inflammatory bowel disease, we did not find a significant association with intestinal permeability. In an untargeted genome-wide association analysis, the top 100 associations were located in 22 genomic loci, although they were not statistically significant after correction for multiple testing (raw P values [1.8 × 10-7 - 1.4 × 10-5]. The lowest P value was obtained for rs9616637 (22q13.33, C22orf34), for which the minor allele A was associated with a decreased LacMan ratio. These results suggest that host genetic background has limited contribution toward intestinal permeability. Despite this, our study is currently the largest of its kind assessing gut permeability in vivo. It remains possible that smaller genetic effect sizes on LacMan ratio are not detectable in this sized cohort. Larger studies are warranted to identify the potential genetic contribution to intestinal permeability.

Gut Microbiota in Patients With Irritable Bowel Syndrome-A Systematic Review

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is common but difficult to treat. Altering the gut microbiota has been proposed as a strategy for treatment of IBS, but the association between the gut microbiome and IBS symptoms has not been well established. We performed a systematic review to explore evidence for this association.

METHODS

We searched databases, including MEDLINE, EMBASE, Cochrane CDSR, and CENTRAL, through April 2, 2018 for case-control studies comparing the fecal or colon microbiomes of adult or pediatric patients with IBS with microbiomes of healthy individuals (controls). The primary outcome was differences in specific gut microbes between patients with IBS and controls.

RESULTS

The search identified 2631 citations; 24 studies from 22 articles were included. Most studies evaluated adults presenting with various IBS subtypes. Family Enterobacteriaceae (phylum Proteobacteria), family Lactobacillaceae, and genus Bacteroides were increased in patients with IBS compared with controls, whereas uncultured Clostridiales I, genus Faecalibacterium (including Faecalibacterium prausnitzii), and genus Bifidobacterium were decreased in patients with IBS. The diversity of the microbiota was either decreased or not different in IBS patients compared with controls. More than 40% of included studies did not state whether cases and controls were comparable (did not describe sex and/or age characteristics).

CONCLUSIONS

In a systematic review, we identified specific bacteria associated with microbiomes of patients with IBS vs controls. Studies are needed to determine whether these microbes are a product or cause of IBS.

Evaluating probiotics for the prevention of ventilator-associated pneumonia: a randomised placebo-controlled multicentre trial protocol and statistical analysis plan for PROSPECT

INTRODUCTION

Ventilator-associated pneumonia (VAP) is the most common healthcare-associated infection in critically ill patients. Prior studies suggest that probiotics may reduce VAP and other infections in critically ill patients; however, most previous randomised trials were small, single centre studies. The Probiotics: Prevention of Severe Pneumonia and Endotracheal Colonization Trial (PROSPECT) aims to determine the impact of the probiotic Lactobacillus rhamnosus GG on VAP and other clinically important outcomes in critically ill adults.

METHODS

PROSPECT is a multicentre, concealed, randomised, stratified, blinded, controlled trial in patients ≥18 years old, anticipated to be mechanically ventilated ≥72 hours, in intensive care units (ICUs) in Canada, the USA and Saudi Arabia. Patients receive either 1×10¹⁰ colony forming units of L. rhamnosus GG twice daily or an identical appearing placebo. Those at increased risk of probiotic infection are excluded. The primary outcome is VAP. Secondary outcomes are other ICU-acquired infections including Clostridioides difficile infection, diarrhoea (including antibiotic-associated diarrhoea), antimicrobial use, ICU and hospital length of stay and mortality. The planned sample size of 2650 patients is based on an estimated 15% VAP rate and will provide 80% power to detect a 25% relative risk reduction.

ETHICS AND DISSEMINATION

This protocol and statistical analysis plan outlines the methodology, primary and secondary analyses, sensitivity analyses and subgroup analyses. PROSPECT is approved by Health Canada (#9427-M1133-45C), the research ethics boards of all participating hospitals and Public Health Ontario. Results will be disseminated via academic channels (peer reviewed journal publications, professional healthcare fora including international conferences) and conventional and social media. The results of PROSPECT will inform practice guidelines worldwide.

TRIALREGISTRATION NUMBER

NCT02462590; Pre-results.

How do probiotics and prebiotics function at distant sites?

The realisation that microbes regarded as beneficial to the host can impart effects at sites distant from their habitat, has raised many possibilities for treatment of diseases. The objective of a workshop hosted in Turku, Finland, by the International Scientific Association for Probiotics and Prebiotics, was to assess the evidence for these effects and the extent to which early life microbiome programming influences how the gut microbiota communicates with distant sites. In addition, we examined how probiotics and prebiotics might affect the skin, airways, heart, brain and metabolism. The growing levels of scientific and clinical evidence showing how microbes influence the physiology of many body sites, leads us to call for more funding to advance a potentially exciting avenue for novel therapies for many chronic diseases.