Prominent members of the human gut microbiota express endo-acting O-glycanases to initiate mucin breakdown.

The thick mucus layer of the gut provides a barrier to infiltration of the underlying epithelia by both the normal microbiota and enteric pathogens. Some members of the microbiota utilise mucin glycoproteins as a nutrient source, but a detailed understanding of the mechanisms used to breakdown these complex macromolecules is lacking. Here we describe the discovery and characterisation of endo-acting enzymes from prominent mucin-degrading bacteria that target the polyLacNAc structures within oligosaccharide side chains of both animal and human mucins. These O-glycanases are part of the large and diverse glycoside hydrolase 16 (GH16) family and are often lipoproteins, indicating that they are surface located and thus likely involved in the initial step in mucin breakdown. These data provide a significant advance in our knowledge of the mechanism of mucin breakdown by the normal microbiota. Furthermore, we also demonstrate the potential use of these enzymes as tools to explore changes in O-glycan structure in a number of intestinal disease states.

Immunosuppression-induced clonal T-cell lymphoproliferative disease causing severe diarrhoea mimicking coeliac disease following renal transplantation: a case report.

BACKGROUND: Post-transplant lymphoproliferative disease is a recognized complication following solid organ transplantation. This is usually a B cell disease and frequently associated with Epstein Barr virus infection, although T cell PTLD can occur. T cell PTLD is usually a monomorphic, lymphomatous disease associated with an adverse prognosis. CASE REPORT: We report a 52 year old male pre-emptive renal transplant recipient who developed severe diarrhea with weight loss following intensification of his immunosuppression due to antibody mediated rejection 3 years after transplantation. Duodenal biopsy demonstrated monoclonal CD8+ T cell duodenitis leading to increased intraepithlieal lymphocytes and sub-total villous atrophy mimicking coeliac disease. Coeliac disease was excluded by negative anti-tissue transglutaminase antibody, HLA-DQ2 and HLA-DQ8 testing. There was no evidence of lymphoma either on biopsy or CT enterography and no FDG avid disease on PET. Symptoms did not improve with reduction of immunosuppression, but resolved fully on complete withdrawal of treatment. The transplant failed and he was established on dialysis. The diagnosis was early PTLD. CONCLUSIONS: Oesophagogastroduodenoscopy with small bowel biopsies is a useful investigation for determining the cause of diarrhoea in renal transplant patients when more common causes have been excluded. This is the first report that we are aware of clonal T cell PTLD mimicking coeliac disease which only resolved after complete withdrawal of immunosuppression. As treatments for lymphoma are aggressive they are only initiated in the malignant phase and management of early stage PTLD is to minimise risk of progression by reducing immunosuppression. Any plans to retransplant will have to take into consideration the possibility that PTLD will recur.

A novel panel of short mononucleotide repeats linked to informative polymorphisms enabling effective high volume low cost discrimination between mismatch repair deficient and proficient tumours.

Somatic mutations in mononucleotide repeats are commonly used to assess the mismatch repair status of tumours. Current tests focus on repeats with a length above 15bp, which tend to be somatically more unstable than shorter ones. These longer repeats also have a substantially higher PCR error rate, and tests that use capillary electrophoresis for fragment size analysis often require expert interpretation. In this communication, we present a panel of 17 short repeats (length 7-12bp) for sequence-based microsatellite instability (MSI) testing. Using a simple scoring procedure that incorporates the allelic distribution of the mutant repeats, and analysis of two cohort of tumours totalling 209 samples, we show that this panel is able to discriminate between MMR proficient and deficient tumours, even when constitutional DNA is not available. In the training cohort, the method achieved 100% concordance with fragment analysis, while in the testing cohort, 4 discordant samples were observed (corresponding to 97% concordance). Of these, 2 showed discrepancies between fragment analysis and immunohistochemistry and one was reclassified after re-testing using fragment analysis. These results indicate that our approach offers the option of a reliable, scalable routine test for MSI.

Do non-targeted gastric biopsies affect the management of patients, and can a simple protocol and education reduce the rate?

OBJECTIVE: To determine whether development of localised protocol could reduce the number of non-targeted gastric biopsies taken at endoscopy, without risking harm from non-detection of malignant conditions. DESIGN: Retrospective analysis of patient records over a 3-month period in 2013, repeated in 2015 following intervention. SETTING: Two UK teaching hospitals. PATIENTS: Patient record data on indication for endoscopy, endoscopy findings, histopathology results and patient outcome. INTERVENTIONS: Guidance on upper gastrointestinal biopsy in the form of a new trust-wide protocol, as well as lecture-based education. MAIN OUTCOME MEASURES: Rates of non-targeted and targeted biopsies before and after intervention, and differences between grade of endoscopist. RESULTS: Between 2013 and 2015, there was a 36% reduction in non-targeted biopsies (10.4% vs 6.7%, p=0.001), predominantly within registrar and nurse endoscopist groups, with reduction in non-targeted biopsies of 9.5% and 64%, respectively. Percentage of targeted biopsies remained relatively static, 7.9% and 8.2%. In 2013, 92% of non-targeted biopsies had no management change based on histology; in 2015 this was 90%. Of patients with alteration to management, only 0.4% and 0.7% were due to malignancy, in known high-risk patients. Reduction in non-targeted biopsies resulted in estimated annual savings in this trust of £36,000. CONCLUSION: Development of local protocol reduces the numbers of non-targeted biopsies taken, without risk of harm from non-detection of malignant conditions, enabling a significant reduction in workload within busy histopathology services, with significant cost savings. Localised protocols are adaptable to local population demographics.

Fatal gastrointestinal histoplasmosis 15 years after orthotopic liver transplantation.

We report a case of ileo-colonic Histoplasmosis without apparent respiratory involvement in a patient who had previously undergone an orthotopic liver transplant (OLT) for primary biliary cholangitis 15 years earlier. The recipient lived in the United Kingdom, a non-endemic region for Histoplasmosis. However, she had previously lived in rural southern Africa prior to her OLT. The patient presented with iron deficiency anaemia, diarrhoea, abdominal pain and progressive weight loss. She reported no previous foreign travel, however, it later became known that following her OLT she had been on holiday to rural southern Africa. On investigation, a mild granulomatous colitis primarily affecting the right colon was identified, that initially improved with mesalazine. Her symptoms worsened after 18 mo with progressive ulceration of her distal small bowel and right colon. Mycobacterial, Yersinia, cytomegalovirus and human immunodeficiency virus infections were excluded and the patient was treated with prednisolone for a working diagnosis of Crohn's disease. Despite some early symptom improvement following steroids, there was subsequent deterioration with the patient developing gram-negative sepsis and multi-organ failure, leading to her death. Post-mortem examination revealed that her ileo-colonic inflammation was caused by Histoplasmosis.

Mitochondrial DNA mutations in human colonic crypt stem cells.

The mitochondrial genome encodes 13 essential subunits of the respiratory chain and has remarkable genetics based on uniparental inheritance. Within human populations, the mitochondrial genome has a high rate of sequence divergence with multiple polymorphic variants and thus has played a major role in examining the evolutionary history of our species. In recent years it has also become apparent that pathogenic mitochondrial DNA (mtDNA) mutations play an important role in neurological and other diseases. Patients harbor many different mtDNA mutations, some of which are mtDNA mutations, some of which are inherited, but others that seem to be sporadic. It has also been suggested that mtDNA mutations play a role in aging and cancer, but the evidence for a causative role in these conditions is less clear. The accumulated data would suggest, however, that mtDNA mutations occur on a frequent basis. In this article we describe a new phenomenon: the accumulation of mtDNA mutations in human colonic crypt stem cells that result in a significant biochemical defect in their progeny. These studies have important consequences not only for understanding of the finding of mtDNA mutations in aging tissues and tumors, but also for determining the frequency of mtDNA mutations within a cell.