Controlling microbial co-culture based on substrate pulsing can lead to stability through differential fitness advantages.

Microbial consortia are an exciting alternative for increasing the performances of bioprocesses for the production of complex metabolic products. However, the functional properties of microbial communities remain challenging to control, considering the complex interaction mechanisms occurring between co-cultured microbial species. Indeed, microbial communities are highly dynamic and can adapt to changing environmental conditions through complex mechanisms, such as phenotypic diversification. We focused on stabilizing a co-culture of Saccharomyces cerevisiae and Escherichia coli in continuous cultures. Our preliminary data pointed out that transient diauxic shifts could lead to stable co-culture by providing periodic fitness advantages to the yeast. Based on a computational toolbox called MONCKS (for MONod-type Co-culture Kinetic Simulation), we were able to predict the dynamics of diauxic shift for both species based on a cybernetic approach. This toolbox was further used to predict the frequency of diauxic shift to be applied to reach co-culture stability. These simulations were successfully reproduced experimentally in continuous bioreactors with glucose pulsing. Finally, based on a bet-hedging reporter, we observed that the yeast population exhibited an increased phenotypic diversification process in co-culture compared with mono-culture, suggesting that this mechanism could be the basis of the metabolic fitness of the yeast.

North American Society for Pediatric Gastroenterology, Hepatology and Nutrition and the Society for Pediatric Radiology Joint Position Paper on Noninvasive Imaging of Pediatric Pancreatitis: Literature Summary and Recommendations.

ABSTRACT: The reported incidence of pediatric pancreatitis is increasing. Noninvasive imaging, including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), play important roles in the diagnosis, staging, follow-up, and management of pancreatitis in children. In this position paper, generated by members of the Pancreas Committee of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) and the Abdominal Imaging Committee of The Society for Pediatric Radiology (SPR), we review the roles of noninvasive imaging in pediatric acute, acute recurrent, and chronic pancreatitis. We discuss available evidence related to noninvasive imaging, highlighting evidence specific to pediatric populations, and we make joint recommendations for use of noninvasive imaging. Further, we highlight the need for research to define the performance and role of noninvasive imaging in pediatric pancreatitis.

Predictors of Enteral Autonomy in Children with Intestinal Failure: A Multicenter Cohort Study.

OBJECTIVES: In a large cohort of children with intestinal failure (IF), we sought to determine the cumulative incidence of achieving enteral autonomy and identify patient and institutional characteristics associated with enteral autonomy. STUDY DESIGN: A multicenter, retrospective cohort analysis from the Pediatric Intestinal Failure Consortium was performed. IF was defined as severe congenital or acquired gastrointestinal diseases during infancy with dependence on parenteral nutrition (PN) >60 days. Enteral autonomy was defined as PN discontinuation >3 months. RESULTS: A total of 272 infants were followed for a median (IQR) of 33.5 (16.2-51.5) months. Enteral autonomy was achieved in 118 (43%); 36 (13%) remained PN dependent and 118 (43%) patients died or underwent transplantation. Multivariable analysis identified necrotizing enterocolitis (NEC; OR 2.42, 95% CI 1.33-4.47), care at an IF site without an associated intestinal transplantation program (OR 2.73, 95% CI 1.56-4.78), and an intact ileocecal valve (OR 2.80, 95% CI 1.63-4.83) as independent risk factors for enteral autonomy. A second model (n = 144) that included only patients with intraoperatively measured residual small bowel length found NEC (OR 3.44, 95% CI 1.36-8.71), care at a nonintestinal transplantation center (OR 6.56, 95% CI 2.53-16.98), and residual small bowel length (OR 1.04 cm, 95% CI 1.02-1.06 cm) to be independently associated with enteral autonomy. CONCLUSIONS: A substantial proportion of infants with IF can achieve enteral autonomy. Underlying NEC, preserved ileocecal valve, and longer bowel length are associated with achieving enteral autonomy. It is likely that variations in institutional practices and referral patterns also affect outcomes in children with IF.

Natural history of pediatric intestinal failure: initial report from the Pediatric Intestinal Failure Consortium.

OBJECTIVE: To characterize the natural history of intestinal failure (IF) among 14 pediatric centers during the intestinal transplantation era. STUDY DESIGN: The Pediatric Intestinal Failure Consortium performed a retrospective analysis of clinical and outcome data for a multicenter cohort of infants with IF. Entry criteria included infants <12 months receiving parenteral nutrition (PN) for >60 continuous days. Enteral autonomy was defined as discontinuation of PN for >3 consecutive months. Values are presented as median (25th, 75th percentiles) or as number (%). RESULTS: 272 infants with a gestational age of 34 weeks (30, 36) and birth weight of 2.1 kg (1.2, 2.7) were followed for 25.7 months (11.2, 40.9). Residual small bowel length in 144 patients was 41 cm (25.0, 65.5). Diagnoses were necrotizing enterocolitis (71, 26%), gastroschisis (44, 16%), atresia (27, 10%), volvulus (24, 9%), combinations of these diagnoses (46, 17%), aganglionosis (11, 4%), and other single or multiple diagnoses (48, 18%). Prescribed medications included oral antibiotics (207, 76%), H2 blockers (187, 69%), and proton pump inhibitors (156, 57%). Enteral feeding approaches varied among centers; 19% of the cohort received human milk. The cohort experienced 8.9 new catheter-related blood stream infections per 1000 catheter days. The cumulative incidences for enteral autonomy, death, and intestinal transplantation were 47%, 27%, and 26%, respectively. Enteral autonomy continued into the fifth year after study entry. CONCLUSIONS: Children with IF endure significant mortality and morbidity. Enteral autonomy may require years to achieve. Improved medical, nutritional, and surgical management may reduce time on PN, mortality, and need for transplantation.

Nutrition education for pediatric gastroenterology, hepatology, and nutrition fellows: survey of NASPGHAN fellowship training programs.

OBJECTIVES: The aim of the study was to assess the methodology and content of nutrition education during gastroenterology fellowship training and the variability among the different programs. METHODS: A survey questionnaire was completed by 43 fellowship training directors of 62 active programs affiliated to the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition, including sites in the United States, Canada, and Mexico. The data were examined for patterns in teaching methodology and coverage of specific nutrition topics based on level 1 training in nutrition, which is the minimum requirement according to the published North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition fellowship training guidelines. RESULTS: The majority of the teaching was conducted by MD-degree faculty (61%), and most of the education was provided through clinical care experiences. Only 31% of the level 1 nutrition topics were consistently covered by >80% of programs, and coverage did not correlate with the size of the programs. Competency in nutrition training was primarily assessed through questions to individuals or groups of fellows (77% and 65%, respectively). Program directors cited a lack of faculty interested in nutrition and a high workload as common obstacles for teaching. CONCLUSIONS: The methodology of nutrition education during gastroenterology fellowship training is, for the most part, unstructured and inconsistent among the different programs. The minimum level 1 requirements are not consistently covered. The development of core curriculums and learning modules may be beneficial in improving nutrition education.

The novel application of an emerging device for salvage of primary repair in high-risk complex esophageal atresia.

INTRODUCTION: Preservation of native esophagus is a tenet of esophageal atresia (EA) repair. However, techniques for delayed primary anastomosis are severely limited for surgically and medically complex patients at high-risk for operative repair. We report our initial experience with the novel application of the Connect-EA, an esophageal magnetic compression anastomosis device, for salvage of primary repair in 2 high-risk complex EA patients. Compassionate use was approved by the FDA and treating institutions. OPERATIVE TECHNIQUE: Two approaches using the Connect-EA are described - a totally endoscopic approach and a novel hybrid operative approach. To our knowledge, this is the first successful use of a hybrid operative approach with an esophageal magnetic compression device. OUTCOMES: Salvage of delayed primary anastomosis was successful in both patients. The totally endoscopic approach significantly reduced operative time and avoided repeat high-risk operation. The hybrid operative approach salvaged delayed primary anastomosis and avoided cervical esophagostomy. CONCLUSION: The Connect-EA is a novel intervention to achieve delayed primary esophageal repair in complex EA patients with high-risk tissue characteristics and multi-system comorbidities that limit operative repair. We propose a clinical algorithm for use of the totally endoscopic approach and hybrid operative approach for use of the Connect-EA in high-risk complex EA patients.

Myeloid translocation gene family members associate with T-cell factors (TCFs) and influence TCF-dependent transcription.

Canonical Wnt signaling is mediated by a molecular "switch" that regulates the transcriptional properties of the T-cell factor (TCF) family of DNA-binding proteins. Members of the myeloid translocation gene (MTG) family of transcriptional corepressors are frequently disrupted by chromosomal translocations in acute myeloid leukemia, whereas MTG16 may be inactivated in up to 40% of breast cancer and MTG8 is a candidate cancer gene in colorectal carcinoma. Genetic studies imply that this corepressor family may function in stem cells. Given that mice lacking Myeloid Translocation Gene Related-1 (Mtgr1) fail to maintain the secretory lineage in the small intestine, we surveyed transcription factors that might recruit Mtgr1 in intestinal stem cells or progenitor cells and found that MTG family members associate specifically with TCF4. Coexpression of beta-catenin disrupted the association between these corepressors and TCF4. Furthermore, when expressed in Xenopus embryos, MTG family members inhibited axis formation and impaired the ability of beta-catenin and XLef-1 to induce axis duplication, indicating that MTG family members act downstream of beta-catenin. Moreover, we found that c-Myc, a transcriptional target of the Wnt pathway, was overexpressed in the small intestines of mice lacking Mtgr1, thus linking inactivation of Mtgr1 to the activation of a potent oncogene.

Deletion of Mtgr1 sensitizes the colonic epithelium to dextran sodium sulfate-induced colitis.

BACKGROUND & AIMS: The disruption of homeostasis between proliferation and apoptosis in the colonic epithelium contributes to the pathogenesis of human ulcerative colitis. Mice lacking the transcriptional corepressor myeloid translocation gene related-1 (Mtgr1) display impaired secretory cell lineage development in the small intestine and an increase in proliferation in the crypts of both the small and large intestines. Despite the increase in proliferating cells, the colons of Mtgr1-null mice have a normal cell lineage distribution and normal architecture. To uncover colonic phenotypes in Mtgr1(-/-) mice, we stressed the colonic epithelium with low-molecular-weight dextran sodium sulfate (DSS), which is a well-studied model of murine ulcerative colitis. METHODS: Mtgr1-null mice were given 3% DSS in their drinking water for 4 days and the colons examined at various times thereafter for ulceration and for changes in proliferation and apoptosis. RESULTS: Treatment with DSS resulted in severe colitis in Mtgr1(-/-) mice, at least partially due to increased epithelial apoptosis rates. Transplantation of wild-type and Mtgr1-null bone marrow into irradiated wild-type mice demonstrated that the severe DSS-induced ulceration seen in Mtgr1-null mice was due to a colonic, rather than a hematologic, defect. Importantly, the epithelium of DSS-treated Mtgr1-null mice failed to completely regenerate, showing changes consistent with chronic colitis, even 10 weeks after a single DSS treatment. CONCLUSIONS: These findings suggest that Mtgr1 has an important role in crypt survival and regeneration after colonic epithelial ulceration.