The role of bacteria in paralytic shellfish poisoning

Historically the production of paralytic shellfish toxins (PST), has been attributed to dinoflagellates. However, in the last decade, increasing evidence has been presented to indicate the involvement of a wide range of bacterial species including cyanobacteria and heterotrophic bacteria (Gallacher et al., 1997). Several studies investigating bacteria capable of PST production, have identified bacteria associated with dinoflagellates are capable of autonomous PST production (Gallacher et al., 1997). However, more recent research has focussed on the effects of these bacteria on toxin production by dinoflagellates, for which the production of bacterial-free (axenic) cultures is essential to identify whether dinoflagellates are capable of autonomous toxin production, in the absence of bacteria. Many different methods to produce axenic algal cultures have been published, including washing methods and the addition of bacteriolytic compounds. However, efforts to generate axenic dinoflagellate cultures, have been hampered not only by difficulties in removing associated bacteria, but also by the lack of effective methods for assessing the presence of certain bacteria. Traditionally, the absence of bacterial growth on marine media was considered acceptable proof for axenic status. However, as the numbers of bacteria determined by culture methods falls short of numbers detected using microscopy (Akagi et al., 1977), culture methods alone have been deemed inadequate to determine the axenic status of algal cultures. In this study, the production of an axenic dinoflagellate culture was vital, firstly, to assess the effect on dinoflagellate toxin production following removal of all associated bacteria, and secondly, to identify whether original toxicity was restored when the microflora was replaced. Methods to assess the axenic nature of cultures combined traditional methods of culturing, with epifluorescence microscopy, the method now frequently relied upon for axenic confirmation. However, molecular techniques were also included, which allowed the axenic status of dinoflagellate cultures to be confidently determined. The availability of molecular techniques also enabled an assessment of the bacterial diversity associated with original dinoflagellate cultures to be conducted, with culture-based and non culture-based identification systems adopted. This investigation indicated that a diverse range of bacteria were associated with cultures, although discrepancies between the two detection methods were noted. Results from the assessment of axenic dinoflagellate cultures confirmed the need for molecular methods, as bacterial DNA was identified in cultures which were considered axenic cultures using media assessment and epifluorescence microscopy. (Abstract shortened by ProQuest.)

Helicobacter pylori CagA Triggers Expression of the Bactericidal Lectin REG3γ via Gastric STAT3 Activation

Background: Most of what is known about the Helicobacter pylori (H. pylori) cytotoxin, CagA, pertains to a much-vaunted role as a determinant of gastric inflammation and cancer. Little attention has been devoted to potential roles of CagA in the majority of H. pylori infected individuals not showing oncogenic progression, particularly in relation to host tolerance. Regenerating islet-derived (REG)3c encodes a secreted C-type lectin that exerts direct bactericidal activity against Grampositive bacteria in the intestine. Here, we extend this paradigm of lectin-mediated innate immunity, showing that REG3c expression is triggered by CagA in the H. pylori-infected stomach. Methodology/Principal Findings: In human gastric mucosal tissues, REG3c expression was significantly increased in CagApositive, compared to CagA-negative H. pylori infected individuals. Using transfected CagA-inducible gastric MKN28 cells, we recapitulated REG3c induction in vitro, also showing that tyrosine phosphorylated, not unphosphorylated CagA triggers REG3c transcription. In concert with induced REG3c, pro-inflammatory signalling downstream of the gp130 cytokine coreceptor via the signal transducer and activator of transcription (STAT)3 and transcription of two cognate ligands, interleukin(IL)-11 and IL-6, were significantly increased. Exogenous IL-11, but not IL-6, directly stimulated STAT3 activation and REG3c transcription. STAT3 siRNA knockdown or IL-11 receptor blockade respectively abrogated or subdued CagAdependent REG3c mRNA induction, thus demonstrating a requirement for uncompromised signalling via the IL-11/STAT

Redefining intestinal immunity with single-cell transcriptomics.

The intestinal immune system represents the largest collection of immune cells in the body and is continually exposed to antigens from food and the microbiota. Here we discuss the contribution of single-cell transcriptomics in shaping our understanding of this complex system. We consider the impact on resolving early intestine development, engagement with the neighbouring microbiota, diversity of intestinal immune cells, compartmentalisation within the intestines and interactions with non-immune cells. Finally, we offer a perspective on open questions about gut immunity that evolving single-cell technologies are well placed to address

Faecal microbiota transplantation as a treatment for inflammatory bowel disease:A national survey of adult and paediatric gastroenterologists in the UK

Background Interest in the use of faecal microbiota transplantation (FMT) in inflammatory bowel disease (IBD) has increased following outcomes in patients with Clostridioides difficile infection (CDI). While research exploring clinician awareness and attitude towards the use of FMT in CDI has been carried out, data for IBD are currently lacking. Objective To assess the perceptions of gastroenterologists and current practice relating to FMT as a treatment for IBD in the UK. Design A web-based survey (Snap Survey software) was distributed through the British Society of Gastroenterology (BSG) and British Society of Paediatric Gastroenterology, Hepatology and Nutrition e-newsletters, and at the BSG Conference in June 2017. Results 61 respondents completed the survey including presubspecialty trainees, gastroenterology specialists, associate specialists and consultants. Most (95%; n=58) respondents stated that they had heard of FMT being used as a treatment for IBD prior to participating in the survey. Based on current evidence, 34% (n=21) of respondents would consider using FMT in patients with IBD, 26% (n=16) would not and 39% (n=24) were undecided. When asked to rank routes of delivery in terms of preference, nasogastric tube was the least preferred route (39%; n=24) and oral capsule was the most preferred route (34%; n=21). Conclusions A clear majority of UK gastroenterologists recognise FMT as a potential treatment for IBD; however, uptake is limited. A proportion of clinicians would consider FMT in IBD and the majority would consider entering patients into clinical trials. Future work should explore the utility and efficacy of oral FMT capsules in IBD.</p