Gut microbiota biofilms: From regulatory mechanisms to therapeutic targets

Gut microbiota contain communities of viruses, bacteria, fungi, and Eukarya, and live as biofilms. In health, these biofilms adhere to the intestinal mucus surface without contacting the epithelium. Disruptions to the equilibrium between these biofilms and the host may create invasive pathobionts from these commensal communities and contribute to disease pathogenesis. Environmental factors appear to dominate over genetics in determining the shifts in microbiota populations and function, including when comparing microbiota between low-income and industrialized countries. The observations discussed herein carry enormous potential for the development of novel therapies targeting phenotype in microbiota dysbiosis.

Diarrhoea: interventions, consequences and epidemiology in the intensive care unit (DICE-ICU): a protocol for a prospective multicentre cohort study

INTRODUCTION

Diarrhoea is a frequent concern in the intensive care unit (ICU) and is associated with prolonged mechanical ventilation, increased length of ICU stay, skin breakdown and renal dysfunction. However, its prevalence, aetiology and prognosis in the critically ill have been poorly studied. The primary objectives of this study are to determine the incidence, risk factors and consequences of diarrhoea in critically ill adults. The secondary objectives are to estimate the incidence of Clostridium difficile-associated diarrhoea (CDAD) in ICU patients and to validate the Bristol Stool Chart and Bliss Stool Classification System characterising bowel movements in the ICU. Our primary outcome is the incidence of diarrhoea . Our secondary outcomes include: CDAD, ICU and hospital mortality and ICU and hospital length of stay.

METHODS AND ANALYSIS

This international prospective cohort study will enrol patients over 10 weeks in 12 ICUs in Canada, the USA, Poland and Saudi Arabia. We will include all patients 18 years of age and older who are admitted to the ICU for at least 24 hours and follow them daily until ICU discharge. Our primary outcome is the incidence of diarrhoea based on the WHO definition, during the ICU stay. Our secondary outcomes include: CDAD, ICU and hospital mortality and ICU and hospital length of stay. We will use logistic regression to identify factors associated with diarrhoea (as defined using WHO criteria) and the kappa statistic to measure agreement on diarrhoea rates between the WHO definition and the Bristol Stool Chart and Bliss Stool Classification System.

ETHICS AND DISSEMINATION

The protocol has been approved by the research ethics board of all participating centres. The diarrhoea interventions, consequences and epidemiology in the intensive care unit (DICE-ICU) study will generate evidence about diarrhoea and its frequency, predisposing factors and consequences, to inform critical care practice and future research.

LAY SUMMARY

Diarrhoea is a frequent clinical problem for hospitalised patients including those who are critically ill in the ICU. Diarrhoea can cause complications such as skin damage, dehydration and kidney problems. It is not clear how common diarrhoea is in the ICU, the factors that cause it or the best way for clinicians to assess it. The DICE-ICU study is an international prospective observational study to examine the frequency, risk factors and outcomes of diarrhoea during critical illness.

Host immunoglobulin G selectively identifies pathobionts in pediatric inflammatory bowel diseases

BACKGROUND

Inflammatory bowel diseases (IBD) are a group of complex and multifactorial disorders with unknown etiology. Chronic intestinal inflammation develops against resident intestinal bacteria in genetically susceptible hosts. We hypothesized that host intestinal immunoglobulin (Ig) G can be used to identify bacteria involved in IBD pathogenesis.

RESULTS

IgG-bound and -unbound microorganisms were collected from 32 pediatric terminal ileum aspirate washes during colonoscopy [non-IBD (n = 10), Crohn disease (n = 15), and ulcerative colitis (n = 7)], and composition was assessed using the Illumina MiSeq platform. In vitro analysis of invasive capacity was evaluated by fluorescence in situ hybridization and gentamicin invasion assay; immune activation was measured by qPCR. Despite considerable inter-individual variations, IgG binding favored specific and unique mucosa-associated species in pediatric IBD patients. Burkholderia cepacia, Flavonifractor plautii, and Rumminococcus sp. demonstrated increased IgG binding, while Pseudomonas ST29 demonstrated reduced IgG binding, in IBD. In vitro validation confirmed that B. cepacia, F. plautii, and Rumminococcus display invasive potential while Pseudomonas protogens did not.

CONCLUSION

Using IgG as a marker of pathobionts in larger patient cohorts to identify microbes and elucidate their role in IBD pathogenesis will potentially underpin new strategies to facilitate development of novel, targeted diagnostic, and therapeutic approaches. Interestingly, this method can be used beyond the scope of this manuscript to evaluate altered gut pathobionts in a number of diseases associated with altered microbiota including arthritis, obesity, diabetes mellitus, alcoholic liver disease, cirrhosis, metabolic syndrome, and carcinomas.

Syntaxin 2 Acts as Inhibitory SNARE for Insulin Granule Exocytosis

Of the four syntaxins specialized for exocytosis, syntaxin (Syn)-2 is the least understood. In this study, we used Syn-2/epimorphin knockout mice to examine the role of Syn-2 in insulin secretory granule (SG) exocytosis. Unexpectedly, Syn-2 knockout mice exhibited paradoxical superior glucose homeostasis resulting from an enhanced insulin secretion. This was confirmed in vitro by pancreatic islet perifusion showing an amplified biphasic glucose-stimulated insulin secretion arising from an increase in size of the readily releasable pool of insulin SGs and enhanced SG pool refilling. The increase in insulin exocytosis was attributed mainly to an enhanced recruitment of the larger pool of newcomer SGs that undergoes no residence time on plasma membrane before fusion and, to a lesser extent, also the predocked SGs. Consistently, Syn-2 depletion resulted in a stimulation-induced increase in abundance of exocytotic complexes we previously demonstrated as mediating the fusion of newcomer SGs (Syn-3/VAMP8/SNAP25/Munc18b) and predocked SGs (Syn-1A/VAMP2/SNAP25/Muncn18a). This work is the first to show in mammals that Syn-2 could function as an inhibitory SNARE protein that, when relieved, could promote exocytosis in pancreatic islet β-cells. Thus, Syn-2 may serve as a potential target to treat diabetes.

The incremental benefit of EUS for identifying unresectable disease among adults with pancreatic adenocarcinoma: A meta-analysis

Background and study aims

It is unclear to what extent EUS influences the surgical management of patients with pancreatic adenocarcinoma. This systematic review sought to determine if EUS evaluation improves the identification of unresectable disease among adults with pancreatic adenocarcinoma.

Patients and methods

We searched MEDLINE, EMBASE, bibliographies of included articles and conference proceedings for studies reporting original data regarding surgical management and/or survival among patients with pancreatic adenocarcinoma, from inception to January 7th 2017. Our main outcome was the incremental benefit of EUS for the identification of unresectable disease (IB_EUS). The pooled IB_EUS were calculated using random effects models. Heterogeneity was explored using stratified meta-analysis and meta-regression.

Results

Among 4,903 citations identified, we included 8 cohort studies (study periods from 1992 to 2007) that examined the identification of unresectable disease (n = 795). Random effects meta-analysis suggested that EUS alone identified unresectable disease in 19% of patients (95% confidence interval [CI], 10–33%). Among those studies that considered portal or mesenteric vein invasion as potentially resectable, EUS alone was able to identify unresectable disease in 14% of patients (95% CI 8–24%) after a CT scan was performed.

Limitations

The majority of the included studies were retrospective.

Conclusions

EUS evaluation is associated with increased identification of unresectable disease among adults with pancreatic adenocarcinoma.