Genomics approach to the analysis of bacterial communities dynamics in Hirschsprung's disease-associated enterocolitis: a pilot study

Hirschsprung-associated enterocolitis: a comprehensive review

Hirschsprung-associated enterocolitis (HAEC) is an important cause of morbidity and the leading cause of mortality in patients with Hirschsprung disease. The pathophysiology of disease includes dysmotility of the enteric nervous system, dysbiosis of the microbiota, failure of the intestinal barrier, and impaired immunity. Common manifestations include fever, abdominal distension, lethargy, vomiting, and diarrhea. Given the non-specific signs and symptoms of HAEC, high clinical suspicion is warranted, especially in patients with risk factors. Diagnosis and management of HAEC depend on the severity of disease presentation. Several preoperative and postoperative modalities have been explored to prevent HAEC. The current review elaborates on the risk factors, pathogenesis, diagnosis, treatment, and prevention of HAEC.

A unicentric cross-sectional observational study on chronic intestinal inflammation in total colonic aganglionosis: beware of an underestimated condition

BACKGROUND

Inflammatory Bowel Diseases (IBD) are known to occur in association with Hirschsprung disease (HSCR). Most of cases are represented by Crohn Disease (CD) occurring in patients with Total Colonic Aganglionosis (TCSA) with an estimated prevalence of around 2%. Based on these considerations and on a number of provisional data belonging to our Center for Digestive Diseases, we developed a unicentric cross-sectional observational study aimed at describing phenotype, genotype, pathology and metagenomics of all patients with TCSA and Crohn-like lesions.

RESULTS

Out of a series of 62 eligible TCSA patients, 48 fulfilled inclusion criteria and were enrolled in the study. Ten patients did not complete the study due to non-compliance or withdrawal of consent and were subsequently dropped out. A total of 38 patients completed the study. All patients were tested for chronic intestinal inflammation by a combination of fecal calprotectine (FC) or occult fecal blood (OFB) and underwent fecal metagenomics. Nineteen (50%) tested positive for FC, OFB, or both and subsequently underwent retrograde ileoscopy. Fourteen patients (36.8%) presented Crohn-like lesions, occurring after a median of 11.5 years after surgery (range 8 months - 21.5 years). No statistically significant differences regarding demographic, phenotype and genotype were observed comparing patients with and without lesions, except for need for blood transfusion that was more frequent in those with lesions. Faecal microbiome of patients with lesions (not that of caregivers) was less biodiverse and characterized by a reduction of Bacteroidetes, and an overabundance of Proteobacteria. FC tested negative in 3/14 patients with lesions (21%).

CONCLUSIONS

Our study demonstrated an impressive 10-folds higher incidence of chronic inflammation in TCSA. Up to 50% of patients may develop IBD-like lesions postoperatively. Nonetheless, we failed in identifying specific risk factors to be used to implement prevention strategies. Based on the results of our study, we suggest screening all TCSA patients with retrograde ileoscopy regardless of FC/OFB values. The frequency of endoscopic assessments and the role of FC/OFB screening in prompting endoscopy is yet to be determined.

Hirschsprung-Associated Enterocolitis: Transformative Research from Bench to Bedside

Hirschsprung disease (HSCR) is a congenital disease that is characterized by the absence of intrinsic ganglion cells in the submucosal and myenteric plexuses of the distal colon and is the most common cause of congenital intestinal obstruction. Hirschsprung-associated enterocolitis (HAEC) is a life-threatening complication of HSCR, which can occur either before or after surgical resection of the aganglionic bowel. Even though HAEC is a leading cause of death in HSCR patients, its etiology and pathophysiology remain poorly understood. Various factors have been associated with HAEC, including the mucus barrier, microbiota, immune function, obstruction of the colon, and genetic variations. In this review, we examine our current mouse model of HAEC and how it informs our understanding of the disease. We also describe current emerging research that highlights the potential future of HAEC treatment.

Different Fecal Microbiota in Hirschsprung's Patients With and Without Associated Enterocolitis

Background and Objectives

Patients with Hirschsprung's disease are at risk of developing Hirschsprung-associated enterocolitis, especially in the first 2 years of life. The pathophysiology of this inflammatory disease remains unclear, and intestinal dysbiosis has been proposed in the last decade. The primary objective of this study was to evaluate in a large cohort if Hirschsprung-associated enterocolitis was associated with alterations of fecal bacterial composition compared with HD without enterocolitis in different age groups.

Methods

We analyzed the fecal microbiota structure of 103 Hirschsprung patients from 3 months to 16 years of age, all of whom had completed definitive surgery for rectosigmoid Hirschsprung. 16S rRNA gene sequencing allowed us to compare the microbiota composition between Hirschsprung's disease patients with (HAEC group) or without enterocolitis (HD group) in different age groups (0-2, 2-6, 6-12, and 12-16 years).

Results

Richness and diversity increased with age group but did not differ between HD and HAEC patients, irrespective of the age group. Relative abundance of Actinobacteria was lower in HAEC than in HD patients under 2 years of age (-66%, P = 0.045). Multivariate analysis by linear models (MaAsLin) considering sex, medications, birth mode, breast-feeding, and the Bristol stool scale, as well as surgery parameters, highlighted Flavonifractor plautii and Eggerthella lenta, as well as Ruminococcus gnavus group, as positively associated with Hirschsprung-associated enterocolitis in the 0-2 years age group.

Conclusion

Hirschsprung-associated enterocolitis was associated with features of intestinal dysbiosis in infants (0-2 years) but not in older patients. This could explain the highest rate of enterocolitis in this age group.

Clinical Trial Registration

https://clinicaltrials.gov/ct2/show/NCT02857205, MICROPRUNG, NCT02857205, 02/08/2016.

Current understanding of Hirschsprung-associated enterocolitis: Pathogenesis, diagnosis and treatment

Hirschsprung-associated enterocolitis (HAEC) was described in 1886 by Harald Hirschsprung and is a potentially deadly complication of Hirschsprung Disease. HAEC is classically characterized by abdominal distension, fever, and diarrhea, although there can be a variety of other associated symptoms, including colicky abdominal pain, lethargy, and the passage of blood-stained stools. HAEC occurs both pre-operatively and post-operatively, is the presenting symptom of HSCR in up to 25% of infants and varies in overall incidence from 20 to 60%. This article reviews our current understanding of HAEC pathogenesis, diagnosis, and treatment with discussion of areas of ongoing research, controversy, and future investigation.

Pathways and microbiome modifications related to surgery and enterocolitis in Hirschsprung disease

BACKGROUND

Hirschsprung disease (HSCR) is a congenital anomaly of the enteric nervous system. Abnormal microbiome composition was reported in HSCR patients. In this study, we addressed and analyzed microbiome modifications with relation tosurgery and HSCR associated enterocolitis (HAEC).

METHODS

The faecal microbiome of 31 HSCR patients (overall 64 samples) was analyzed. HAEC was diagnosed and classified according to a combination of Pastor's and Elhalabi's criteria. Stool samples were analyzed by 16S sequencing (7 out of 9 polymorphic regions). Compositional and relative abundance profiles, as well as the functional potentials of the microbial community, were analyzed with the marker gene sequencing profiles using PICRUSt.

RESULTS

The relative abundance of Bacteroidetes showed a severe decrease with slow recovery after surgery. Conversely, Proteobacteria transiently increased their abundance. Noteworthy, a strong linkage has been found between Proteobacteria descendants and HAEC occurrences. The inferred functional analysis indicated that virulence factors and fimbriae or pili might be associated with HAEC.

CONCLUSIONS

Our study, addressing microbiome dynamics, demonstrated relevant changes after surgical manipulation. Alpha-diversity analyses indicated that surgery deeply affects microbiome composition. Proteobacteria and Enterobacteriaceae seem to play a pivotal role in HAEC occurrences. Several virulence factors, such as fimbriae or pili, might explain the HAEC-predisposing potential of selected microbiomes. These results suggest some innovative therapeutic approaches that deserve to be tested in appropriate clinical trials.

Associations of SLC6A20 genetic polymorphisms with Hirschsprung's disease in a Southern Chinese population

Hirschsprung's disease (HSCR) is a neurodevelopmental disorder characterized by the absence of nerves in intestine with strong genetic components. SLC6A20 was found to be associated with HSCR in Korean population waiting for replication in an independent cohort. In the present study, ten single nucleotide polymorphisms (SNPs) in the SLC6A20 were selected from Southern Chinese with 1470 HSCR cases and 1473 ethnically matched healthy controls. Our results indicated that SNP rs7640009 was associated with HSCR and SLC6A20 has a gene-dose effect in the extent of the aganglionic segment during enteric nervous system (ENS) development. It is the first time to reveal the relationship between SNP rs2191026 and HSCR-associated enterocolitis (HAEC) susceptibility.

A Metagenomics Study on Hirschsprung's Disease Associated Enterocolitis: Biodiversity and Gut Microbial Homeostasis Depend on Resection Length and Patient's Clinical History

Objectives: Since 2010, several researches demonstrated that microbiota dynamics correlate and can even predispose to Hirschsprung (HSCR) associated enterocolitis (HAEC). This study aims at assessing the structure of the microbiota of HSCR patients in relation to extent of aganglionosis and HAEC status. Methods: All consecutive HSCR patients admitted to Gaslini Institute (Genova, Italy) between May 2012 and November 2014 were enrolled. Institutional review board (IRB) approval was obtained. Stools were sampled and 16S rDNA V3-V4 regions were sequenced using the Illumina-MiSeq. Taxonomy assignments were performed using QIIME RDP. Alpha diversity indexes were analyzed by Shannon and Simpson Indexes, and Phylogenetic Diversity. Results: We enrolled 20 patients. Male to female ratio was 4:1. Six patients suffered from Total Colonic Aganglionosis (TCSA). Considering sample site (i.e., extent of aganglionosis), we confirmed the known relationship between sample site and both biodiversity and composition of intestinal microbiota. Patients with TCSA showed lower biodiversity and increased Proteobacteria/Bacteroidetes relative abundance ratio. When addressing biodiversity, composition and dynamics of TCSA patients we could not find any significant relationship with regard to HAEC occurrences. Conclusions: The composition of HAEC predisposing microbiota is specific to each patient. We could confirm that total colon resections can change the composition of intestinal microbiota and to dramatically reduce microbial diversity. The subsequent reduction of system robustness could expose TCSA patients to environmental microbes that might not be part of the normal microbiota. Future long-term studies should investigate both patients and their family environment, as well as their disease history.

Bacterial Microbiome Dynamics in Post Pull-Through Hirschsprung-Associated Enterocolitis (HAEC): An Experimental Study Employing the Endothelin Receptor B-Null Mouse Model

PURPOSE

Hirschsprung-associated enterocolitis (HAEC) is the most frequent potentially life-threatening complication in children with Hirschsprung disease (HSCR) even after definitive corrective surgery. Mounting evidence suggests that intestinal microbiota likely contribute to the etiology of enterocolitis, so the aim of this study was to use a mouse model of post pull-through HAEC to compare the fecal bacterial communities of animals which developed HAEC to those free of enterocolitis.

METHODS

Ten Ednrb -/- and 8wild type mice underwent the microsurgical pull-through surgery, and stool was collected at the time of surgery, and then either at 2 and 4 weeks after the operation, or when the mice developed enterocolitis. The mid-colon of all animals was collected, prepared and histologically graded for enterocolitis. Fecal DNA was isolated and bacterial 16S rRNA genes analyzed using Illumina sequencing.

RESULTS

Six Ednrb-/- mice developed HAEC with a mean enterocolitis score of 5.7, while the remaining 4 mutant and 8 WT mice remained free of enterocolitis by 4 weeks. The HAEC group had lower alpha diversity by Chao1 analysis compared with WT group, while the Ednrb-/- mice demonstrated distinct bacterial communities from WT mice on beta diversity analysis. The most striking finding was increased proportion of Akkermansia and reduced Bacteroidetes compared with the NO HAEC and WT groups, suggesting Akkermansia may contribute to development of enterocolitis while Bacteroidetes may be protective. Less abundant genera that were reduced in HAEC were Dysgonomas and Clostridium XIVa which may play a protective role.

CONCLUSIONS

This is the first study to identify Akkermansia as potentially playing a role in HAEC, either as a pathobiont taxa contributing to pathogenesis of enterocolitis, or possibly a protective commensal taxa expanded in response to inflammation. These findings characterized the dynamic shifts in the gut microbial communities through the onset of post pull-through HAEC, and suggests that there may be identifiable bacterial community differences in HSCR patients that are high risk for developing HAEC.

Characterization of Intestinal Microbiomes of Hirschsprung's Disease Patients with or without Enterocolitis Using Illumina-MiSeq High-Throughput Sequencing

Hirschsprung-associated enterocolitis (HAEC) is a life-threatening complication of Hirschsprung's disease (HD). Although the pathological mechanisms are still unclear, studies have shown that HAEC has a close relationship with the disturbance of intestinal microbiota. This study aimed to investigate the characteristics of the intestinal microbiome of HD patients with or without enterocolitis. During routine or emergency surgery, we collected 35 intestinal content samples from five patients with HAEC and eight HD patients, including three HD patients with a history of enterocolitis who were in a HAEC remission (HAEC-R) phase. Using Illumina-MiSeq high-throughput sequencing, we sequenced the V4 region of bacterial 16S rRNA, and operational taxonomic units (OTUs) were defined by 97% sequence similarity. Principal coordinate analysis (PCoA) of weighted UniFrac distances was performed to evaluate the diversity of each intestinal microbiome sample. The microbiota differed significantly between the HD patients (characterized by the prevalence of Bacteroidetes) and HAEC patients (characterized by the prevalence of Proteobacteria), while the microbiota of the HAEC-R patients was more similar to that of the HAEC patients. We also observed that the specimens from different intestinal sites of each HD patient differed significantly, while the specimens from different intestinal sites of each HAEC and HAEC-R patient were more similar. In conclusion, the microbiome pattern of the HAEC-R patients was more similar to that of the HAEC patients than to that of the HD patients. The HD patients had a relatively distinct, more stable community than the HAEC and HAEC-R patients, suggesting that enterocolitis may either be caused by or result in a disruption of the patient's uniquely adapted intestinal flora. The intestinal microbiota associated with enterocolitis may persist following symptom resolution and can be implicated in the symptom recurrence.

Established and Emerging Concepts in Hirschsprung’s-Associated Enterocolitis

Hirschsprung's disease (HSCR) is a common cause of neonatal bowel obstruction and the approach to diagnosis and surgical treatment is well defined and accepted. Hirschsprung's-associated enterocolitis (HAEC) remains a frequent cause of pre-operative and post-operative morbidity and mortality, with unchanged treatment guidelines over multiple decades. Recent advances in our understanding of the genetics underlying HSCR have allowed the development of animal models, some of which recapitulate the HAEC phenotype. These animal models, along with recent translational studies, have implicated multiple facets of mucosal immunity and microbiome dysbiosis in the development of HAEC. Here, we will review the established epidemiology, modes of diagnosis and treatment of HAEC. Furthermore, we will explore emerging concepts in the pathogenesis of this disease; including animal models, alterations in mucosal immunity, dysbiosis of the intestinal microbiome, specific genetic susceptibility, and novel treatment modalities.

Dynamic changes in microbiota and mycobiota during spontaneous 'Vino Santo Trentino' fermentation

Vino Santo is a sweet wine produced from late harvesting and pressing of Nosiola grapes in a small, well-defined geographical area in the Italian Alps. We used metagenomics to characterize the dynamics of microbial communities in the products of three wineries, resulting from spontaneous fermentation with almost the same timing and procedure. Comparing fermentation dynamics and grape microbial composition, we show a rapid increase in a small number of wine yeast species, with a parallel decrease in complexity. Despite the application of similar protocols, slight changes in the procedures led to significant differences in the microbiota in the three cases of fermentation: (i) fungal content of the must varied significantly in the different wineries, (ii) Pichia membranifaciens persisted in only one of the wineries, (iii) one fermentation was characterized by the balanced presence of Saccharomyces cerevisiae and Hanseniaspora osmophila during the later phases. We suggest the existence of a highly winery-specific 'microbial-terroir' contributing significantly to the final product rather than a regional 'terroir'. Analysis of changes in abundance during fermentation showed evident correlations between different species, suggesting that fermentation is the result of a continuum of interaction between different species and physical-chemical parameters.

Exome sequencing reveals a high genetic heterogeneity on familial Hirschsprung disease

Hirschsprung disease (HSCR; OMIM 142623) is a developmental disorder characterized by aganglionosis along variable lengths of the distal gastrointestinal tract, which results in intestinal obstruction. Interactions among known HSCR genes and/or unknown disease susceptibility loci lead to variable severity of phenotype. Neither linkage nor genome-wide association studies have efficiently contributed to completely dissect the genetic pathways underlying this complex genetic disorder. We have performed whole exome sequencing of 16 HSCR patients from 8 unrelated families with SOLID platform. Variants shared by affected relatives were validated by Sanger sequencing. We searched for genes recurrently mutated across families. Only variations in the FAT3 gene were significantly enriched in five families. Within-family analysis identified compound heterozygotes for AHNAK and several genes (N = 23) with heterozygous variants that co-segregated with the phenotype. Network and pathway analyses facilitated the discovery of polygenic inheritance involving FAT3, HSCR known genes and their gene partners. Altogether, our approach has facilitated the detection of more than one damaging variant in biologically plausible genes that could jointly contribute to the phenotype. Our data may contribute to the understanding of the complex interactions that occur during enteric nervous system development and the etiopathology of familial HSCR.

Disruptions of the intestinal microbiome in necrotizing enterocolitis, short bowel syndrome, and Hirschsprung's associated enterocolitis

Next generation sequencing techniques are currently revealing novel insight into the microbiome of the human gut. This new area of research seems especially relevant for neonatal diseases, because the development of the intestinal microbiome already starts in the perinatal period and preterm infants with a still immature gut associated immune system may be harmed by a dysproportional microbial colonization. For most gastrointestinal diseases requiring pediatric surgery there is very limited information about the role of the intestinal microbiome. This review aims to summarize the current knowledge and outline future perspectives for important pathologies like necrotizing enterocolitis (NEC) of the newborn, short bowel syndrome (SBS), and Hirschsprung’s disease associated enterocolitis (HAEC). Only studies applying next generation sequencing techniques to analyze the diversity of the intestinal microbiome were included. In NEC patients intestinal dysbiosis could already be detected prior to any clinical evidence of the disease resulting in a reduction of the bacterial diversity. In SBS patients the diversity seems to be reduced compared to controls. In children with Hirschsprung’s disease the intestinal microbiome differs between those with and without episodes of enterocolitis. One common finding for all three diseases seems to be an overabundance of Proteobacteria. However, most human studies are based on fecal samples and experimental data question whether fecal samples actually represent the microbiome at the site of the diseased bowel and whether the luminal (transient) microbiome compares to the mucosal (resident) microbiome. In conclusion current studies already allow a preliminary understanding of the potential role of the intestinal microbiome in pediatric surgical diseases. Future investigations could clarify the interface between the intestinal epithelium, its immunological competence and mucosal microbiome. Advances in this field may have an impact on the understanding and non-operative treatment of such diseases in infancy.

Impaired Cellular Immunity in the Murine Neural Crest Conditional Deletion of Endothelin Receptor-B Model of Hirschsprung's Disease

Hirschsprung’s disease (HSCR) is characterized by aganglionosis from failure of neural crest cell (NCC) migration to the distal hindgut. Up to 40% of HSCR patients suffer Hirschsprung’s-associated enterocolitis (HAEC), with an incidence that is unchanged from the pre-operative to the post-operative state. Recent reports indicate that signaling pathways involved in NCC migration may also be involved in the development of secondary lymphoid organs. We hypothesize that gastrointestinal (GI) mucosal immune defects occur in HSCR that may contribute to enterocolitis. EdnrB was deleted from the neural crest (EdnrB^NCC-/-) resulting in mutants with defective NCC migration, distal colonic aganglionosis and the development of enterocolitis. The mucosal immune apparatus of these mice was interrogated at post-natal day (P) 21–24, prior to histological signs of enterocolitis. We found that EdnrB^NCC-/- display lymphopenia of their Peyer’s Patches, the major inductive site of GI mucosal immunity. EdnrB^NCC-/- Peyer’s Patches demonstrate decreased B-lymphocytes, specifically IgM⁺IgD^hi (Mature) B-lymphocytes, which are normally activated and produce IgA following antigen presentation. EdnrB^NCC-/- animals demonstrate decreased small intestinal secretory IgA, but unchanged nasal and bronchial airway secretory IgA, indicating a gut-specific defect in IgA production or secretion. In the spleen, which is the primary source of IgA-producing Mature B-lymphocytes, EdnrB^NCC-/- animals display decreased B-lymphocytes, but an increase in Mature B-lymphocytes. EdnrB^NCC-/- spleens are also small and show altered architecture, with decreased red pulp and a paucity of B-lymphocytes in the germinal centers and marginal zone. Taken together, these findings suggest impaired GI mucosal immunity in EdnrB^NCC-/- animals, with the spleen as a potential site of the defect. These findings build upon the growing body of literature that suggests that intestinal defects in HSCR are not restricted to the aganglionic colon but extend proximally, even into the ganglionated small intestine and immune cells.

Hirschsprung's associated enterocolitis

PURPOSE OF REVIEW

Hirschsprung's disease (HSCR) is characterized by an absence of ganglion cells in the distal hindgut, extending from the rectum to a variable distance proximally, and results from a failure of cranial-caudal neural crest cell migration. Hirschsprung's-associated enterocolitis (HAEC) is a condition with classic manifestations that include abdominal distention, fever and foul-smelling stools, and is a significant and life-threatening complication of HSCR. The purpose of this review was to critically evaluate recent findings regarding the pathophysiology of HAEC.

RECENT FINDINGS

Several recent studies have investigated the cause of HAEC in humans and mouse models. These studies suggest that alterations in the intestinal barrier, including goblet cell number and function, and Paneth cell function, impaired gastrointestinal mucosal immunity, including B-lymphocyte trafficking or function and secretory immunoglobulin A production, and dysbiosis of the intestinal microbiota may contribute to the development of HAEC.

SUMMARY

Recent studies add to the body of literature, suggesting that the intestinal defects observed in HSCR are not restricted to the aganglionic segment but extend to the mucosal immune system within and beyond the gastrointestinal tract. Future studies further dissecting the mechanisms of HAEC and validating these findings in humans will allow for the development of directed therapeutic interventions.

Probiotics prevent Hirschsprung's disease-associated enterocolitis: a prospective multicenter randomized controlled trial

BACKGROUND

Enterocolitis (EC) is the most common and serious postoperative complication of Hirschsprung's disease (HD). Probiotics potentially play a protective role in maintaining intestinal mucosal integrity. Based on the beneficial effects of probiotics, we hypothesized that oral probiotics could decrease the incidence and severity of Hirschsprung's disease-associated enterocolitis (HAEC).

METHODS

We conducted a prospective, multicenter, randomized, and controlled trial to assess whether oral probiotics could decrease the incidence and severity of HAEC. HD patients were randomly assigned into the control group and probiotic-treated group. All children in probiotic-treated group were fed with probiotics per day for 4 weeks. In next 3 months, the incidence and severity of HAEC were analyzed. The peripheral blood T lymphocyte subsets and cytokines, including TNF-α, IFN-γ, IL-6, and IL-10, were analyzed by flow cytometry and enzyme immunoassay (EIA).

RESULTS

Compared with the control group, the incidence of HAEC in the probiotic-treated group was significantly diminished. The severity of EC was also remarkably decreased. Furthermore, probiotics balanced T lymphocyte subsets. Moreover, pro-inflammatory cytokines TNF-α, IFN-γ, and IL-6 were significantly decreased and anti-inflammatory cytokine IL-10 was notably increased in probiotic-treated group.

CONCLUSIONS

Probiotics not only significantly diminished the incidence but also decreased the severity of HAEC. Moreover, our study revealed that probiotics decreased pro-inflammatory cytokine and increased anti-inflammatory cytokine and furthermore balanced T lymphocytes (registered with ClinicalTrials.gov, NCT number: NCT01934959).

Intestinal dysbiosis and bacterial enteroinvasion in a murine model of Hirschsprung's disease

BACKGROUND/PURPOSE

Hirschsprung's disease (HSCR), characterized by the absence of ganglia in the distal colon, results in functional obstruction. Despite surgical resection of the aganglionic segment, around 40% of patients suffer recurrent life threatening Hirschsprung's-associated enterocolitis (HAEC). The aim of this study was to investigate whether gut microbiota and intestinal immunity changes contribute to the HAEC risk in an HSCR model.

METHODS

Mice with neural crest conditional deletion of Endothelin receptor B (EdnrB) and their littermate controls were used (EdnrB-null and EdnrB-het). Bacterial DNA was prepared from cecal contents of P16-18 and P21-24 animals and pyrosequencing employed for microbiome analysis. Ileal tissue was isolated and secretory phospholipase A2 (sPLA2) expression and activity determined. Enteroinvasion of Escherichia coli into ileal explants was measured using an ex vivo organ culture system.

RESULTS

EdnrB-het and EdnrB-nulls displayed similar flora, sPLA2 expression and activity at P16-18. However, by P21-24, EdnrB-hets demonstrated increased Lactobacillus and decreased Bacteroides and Clostridium, while EdnrB-nulls exhibited reciprocal changes. EdnrB-nulls also showed reduced sPLA2 expression and luminal activity at this stage. Functionally, EdnrB-nulls were more susceptible to enteroinvasion with E. coli ex vivo and released less sPLA2 than EdnrB-hets.

CONCLUSIONS

Initially, EdnrB-het and EdnrB-nulls contain similar cecal flora but then undergo reciprocal changes. EdnrB-nulls display dysbiosis, demonstrate impaired mucosal defense, decreased luminal sPLA2 and increased enteroinvasion of E. coli just prior to robust colonic inflammation and death. These findings suggest a role for the intestinal microbiome in the development of HAEC.

Recent developments in Hirschsprung's-associated enterocolitis

Hirschsprung's-associated enterocolitis (HAEC) continues to be a significant source of morbidity for patients with Hirschsprung's disease (HD). New clinical and histologic classification systems for HAEC will improve consistency between reports and increase the ability to compare outcomes. A complete understanding of disease pathogenesis is lacking, but evidence suggests that the intestinal microbiota may play a role in the development of HD and HAEC. The benefits of adjunctive therapies, such as anal dilations and botulinum toxin to reduce the incidence of HAEC following corrective endorectal pull-through, remain controversial. Finally, new clinical data have identified an association between HAEC and inflammatory bowel disease and will likely lead to further genetic studies to elucidate the connection between these two disease processes.

Probiotic prophylaxis after pullthrough for Hirschsprung disease to reduce incidence of enterocolitis: a prospective, randomized, double-blind, placebo-controlled, multicenter trial

OBJECTIVE

Hirschsprung-associated enterocolitis (HAEC) is one of the most troublesome problems encountered after a pullthrough. We hypothesized that prophylactic administration of probiotics after a pullthrough procedure would decrease the incidence of HAEC.

STUDY DESIGN

A prospective, double-blind, placebo-controlled, randomized trial was conducted at 2 children's hospitals. Infants undergoing pullthrough were randomized to probiotic or placebo for a period of 3 months post-pullthrough. Primary outcome was incidence of post-operative HAEC. Other outcomes included severity of HAEC by clinical grade, number of HAEC episodes and extent of aganglionosis. Pearson Chi Square analysis, as well as logistic regression, was used for statistical analysis.

RESULTS

Sixty-two patients were recruited (Sites: A=40; B=22). One was lost to follow up and one immediate post-op death was not included in final analysis. Probiotics were administered to 32 patients. Distribution of placebo/probiotics was equal between sites (P=0.858). Mean age at pullthrough was 6.5 ± 8.1(± SD) months. The incidence of HAEC was 28.3%. The incidence of HAEC was not statistically different between probiotic and placebo study groups.

CONCLUSIONS

Incidence of HAEC was not reduced with prophylactic probiotics. Future studies are needed to better determine the etiology and possible ways of preventing this complex condition.

The pathogenesis of Hirschsprung's disease-associated enterocolitis

Hirschsprung's disease-associated enterocolitis (HAEC) remains the most life-threatening complication in Hirschsprung disease (HD) patients. The pathogenesis of HAEC has not been determined and many hypotheses regarding the etiology of HAEC have been proposed. These include a possible causal relationship between the abnormal enteric nervous system development in HD and the development of enterocolitis. Based on the complex genetic causes of HD that have been discovered and the resultant heterogeneous group of patients that exists, the causes of HAEC are likely multiple. New insights regarding the relationship of the role of the enteric nervous system and its interaction between intestinal barrier function, innate host immunity, and commensal microflora have been discovered, which may shed light on this perplexing problem. This review presents current known risk factors of HAEC and the proposed theories and supporting evidence for the potential etiologies of HAEC.

Hirschsprung-associated enterocolitis: prevention and therapy

Hirschsprung-associated enterocolitis remains the greatest cause of morbidity and mortality in children with Hirschsprung disease. This chapter details the various approaches used to treat and prevent this disease process. This includes prevention of complications, such as stricture formation, prophylaxis with rectal washouts, and identification of high-risk individuals. The chapter also details approaches to diagnose Hirschsprung-associated enterocolitis as well as to exclude other etiologies.

Intestinal aganglionosis is associated with early and sustained disruption of the colonic microbiome

BACKGROUND

Congenital aganglionosis (Hirschsprung's disease) results in colonic dysmotility and a risk for Hirschsprung's-associated enterocolitis (HAEC), whose cause is unknown. We hypothesized that aganglionosis leads to microbiome changes that may contribute to HAEC risk.

METHODS

Colon and fecal samples were collected from endothelin receptor B-null (Ednrb(-/-) ) mice, an established model of colorectal aganglionosis, at postnatal day 7 (P7), P20, and P24. We determined microbiome composition by 16S ribosomal RNA gene pyrosequencing and fecal metabolite profile by nuclear magnetic resonance spectroscopy.

KEY RESULTS

Wild-type (WT) mice exhibited increasing species diversity with age, with mutant mice possessing even greater diversity. WT and mutant microbiomes, both fecal and colonic, significantly segregated by principal coordinates analysis based on species composition at all ages examined. Importantly, mutant mice contained more Bacteroidetes and less Firmicutes than WT, with additional genus- and species-level differences observed. Notably, mutant P7 colon was dominated by coagulase-negative Staphylococcus species, which were rare in WT. Mutant fecal metabolite profiles also differed, particularly in the abundance of formate, a short-chain fatty acid product of microbial fermentation.

CONCLUSIONS & INFERENCES

Colorectal aganglionosis is associated with early and sustained disruption of the normal colonic and fecal microbiome, supporting the enteric nervous system as a determinant of microbiome composition. Furthermore, the differences observed suggest a potential contributory role for the microbiome in the etiology of HAEC. These findings provide a basis for further studies to determine the causative role of specific bacterial communities in HAEC and the potential to restore the normal microbiome in Hirschsprung's disease.