Tofacitinib for celiac disease and microscopic colitis: killing two birds with one stone.

Microscopic colitis is a chronic inflammatory condition of the colon. Firstline treatment consists of budesonide, with the consideration of biological agents in refractory cases. Celiac disease is a chronic immune mediated and gluten-induced enteropathy, with treatment consisting of a gluten-free diet. There is an association between microscopic colitis and instead of xand celiac disease, especially in refractory cases they can coincide. In this manuscript, we report for the first time the efficacy of tofacitinib, a pan Janus kinase inhibitor, in the treatment of concomitant microscopic colitis and celiac disease, resulting in persistent clinical and histological remission.

Child with protein losing enteropathy as presentation of collagenous duodenitis and eosinophilic gastroenteritis.

Background: Collagenous duodenitis and gastritis are rare histopathological findings in children. Patients and methods: : We describe a four-year old girl, who presented with non-bloody diarrhea for two months and progressive edema with an albumin of 16g/dl. Results: The diagnosis of a protein losing enteropathy was made. Extensive investigations withheld only an infectious cause of the protein losing enteropathy (cytomegalovirus and adenovirus). However, the patients still required repetitive albumin infusions 3.5 months after onset of symptoms without spontaneous recovery. Therefore, a new endoscopic work-up was performed. Duodenal biopsies revealed collagen deposition, in association with a high number of eosinophils and mast cells throughout different parts of the gastrointestinal tract. Conclusions: The collagen deposition seems to be triggered by an eosinophilic gastrointestinal disorder. Treatment was started with amino acid-based formula, oral iron therapy, an antihistamine, and a proton pomp inhibitor that resulted in persistent normalization of serum albumin already after 1.5 weeks.

Managing metastatic Crohn's disease: a single center experience, review of the current evidence, and treatment algorithm.

BACKGROUND: Crohn's disease (CD) is an inflammatory bowel disease (IBD) that, besides gastrointestinal symptoms, may encompass extra-intestinal symptoms, such as dermatological manifestations. Of those, metastatic CD (MCD) is a rare extra-intestinal manifestation for which the management is uncertain. METHODS: We conducted a retrospective case series of patients with MCD seen at the University hospital Leuven, Belgium, combined with an overview of the recent literature. Electronic medical records were searched from January 2003 till April 2022. For the literature search, Medline, Embase, Trip Database, and The Cochrane Library were searched from inception to April 1, 2022. RESULTS: A total of 11 patients with MCD were retrieved. In all cases noncaseating granulomatous inflammation was found on skin biopsies. Two adults and one child were diagnosed with MCD prior to their diagnosis of CD. Seven patients were treated with steroids (intralesional, topical or systemic). Six patients needed a biological therapy to treat MCD. Surgical excision was performed in three patients. All patients reported a successful outcome and most cases achieved remission. The literature search yielded 53 articles, including three reviews, three systematic reviews, 30 case reports and six case series. A treatment algorithm was generated based on literature and multidisciplinary discussion. CONCLUSION: MCD remains a rare entity and diagnosis is often difficult. A multidisciplinary approach including skin biopsy is necessary to diagnose and treat MCD efficiently. Outcome is generally favorable, and lesions respond well to steroids and biologicals. We propose a treatment algorithm based on the available evidence and multidisciplinary discussion.

Therapeutic outcome of diverticular associated colitis - a retrospective single centre experience.

BACKGROUND: Diverticular associated colitis (DAC) has become increasingly appreciated as a form of inflammatory disease, localized mainly in the sigmoid, and defined as chronic inflammation of the interdiverticular mucosa with sparing of rectum, right colon and diverticula themselves. METHODS: A retrospective case identification from January 2005 to December 2016 was performed. Patients with a diagnosis of DAC based on clinical, endoscopic and histological findings were enrolled. We analyzed their characteristics and response to therapy, and performed a review of literature. RESULTS: Out of 377 pathology reports, 37 cases of DAC were identified, with a median age of 73 years and followed during 1-13 years. Six patients (16.22%) were refractory to conservative treatment and required surgery. In three patients (8.11%) evolution to ulcerative colitis (UC) was observed. Patients were divided into four endoscopic patterns, with a more benign course for type A "crescentic fold disease" compared to the other subtypes. Patients with type B "mild to moderate ulcerative colitis-like" were at significantly higher risk of persistent disease activity or relapse (p < 0.01). CONCLUSION: DAC is a multifaceted disease and considered to be a relatively benign condition. However, a subset of patients requires surgery and/or may progress to develop UC.

Mesenteric panniculitis as a presentation of Whipple's disease: case report and review of the literature.

BACKGROUND: Whipple's disease is a rare, multi-organ disease caused by Tropheryma Whipplei. A classic presentation is characterized by arthropathy, diarrhea and weight loss but a broad spectrum of manifestations is possible. We present a case of a patient with mesenteric panniculitis as a manifestation of WD. A comprehensive review of the literature is provided. PATIENT: A 50 year old male presented at the outpatient clinic after an episode of fever and abdominal pain abroad. CT scan showed mesenteric infiltration with associated lymphadenopathies consistent with mesenteric panniculitis. After receiving 6 months of antibiotic therapy abdominal and joint pains improved. CONCLUSION: Clinicians should be aware of Whipple's disease. Mesenteric panniculitis is a rare presentation of this possible lethal infection. The golden standard for diagnosing WD is a PAS positive small bowel biopsy. Adequate antibiotic therapy is the cornerstone of treatment and usually leads to an amelioration of symptoms.

Appendiceal cancer : a review of the literature.

Primary appendiceal cancer is rare and most commonly found incidentally on a surgical specimen after appendectomy for acute appendicitis. This small organ gives rise to different subtypes which are histological and biological distinct. Historically the classification of these tumors has been confusing because of the different nomenclature that is used. This review has broadly classified them into four subgroups: colonic-type adenocarcinoma, mucinous neoplasm, goblet cell carcinoma and neuroendocrine neoplasm. Signet ring cells is not considered as a distinct subgroup but as a histologic feature that can be present in colonic-type adenocarcinoma and mucinous neoplasms. As staging and management of appendiceal tumors depend on these subtypes, an adequate classification of them is important. This review aimed to give an overview of the epidemiology, grading and staging, management and prognosis of these neoplasms. Despite its rarety, specific staging systems and treatment guidelines exist for some subtypes. For other subtypes staging systems and management is extrapolised from colorectal cancer because of the lack of randomised, prospective trials.

Systematic Review: Histological Scoring of Strictures in Crohn's Disease.

BACKGROUND AND AIMS: In Crohn's disease, many patients develop a stricture, which can due to inflammation, fibrosis and muscular changes or all at the same time. Determining the predominant component has therapeutic consequences but remains challenging. To develop imaging techniques that assess the nature of a stricture, a gold standard is needed and histopathology is considered as such. This paper provides an overview of published histological scoring systems for strictures in Crohn's disease. METHODS: A systematic literature review according to PRISMA guidelines was performed of histological scoring indices that assessed whether a stricture was inflammation-predominant or fibrosis-predominant. Multiple libraries were searched from inception to December 2018. Two reviewers independently assessed abstracts and full-texts. RESULTS: Sixteen articles were identified as suitable for this systematic review. A large number of parameters were reported. Extent of neutrophil infiltration and extent of fibrosis in the bowel wall were most frequently described to reflect severity of inflammation and fibrosis, respectively. Among the 16 studies, only two described a numerical scoring system for the inflammatory and fibrotic component separately. Smooth muscle changes were scored in a minority of studies. CONCLUSIONS: Multiple scoring systems have been developed. There was large heterogeneity in scoring per parameter and construction of numerical scoring systems. Therefore, we feel that none of the systems is suitable to be used as gold standard. We offer an overview of histological parameters that could be incorporated in a future histological scoring index for strictures.

Eosinophilic peak counts in eosinophilic esophagitis : a retrospective study.

BACKGROUND: The histologic diagnosis of eosinophilic esophagitis (EoE) is based on finding >15 eosinophils/high power field (HPF) on any level within the squamous epithelium of the esophagus. However, this criterion is based on a consensus statement, and controversy remains about the exact number of eosinophils/HPF needed to diagnose EoE. We aimed to determine eosinophilic peak counts in esophageal, gastric, and duodenal biopsies from suspected EoE patients, investigate the correlation between eosinophilic peak counts at different biopsy locations, and determine inter-observer and intra-observer reliability in reporting eosinophilic peak counts. METHODS: We selected 103 suspected EoE patients, who underwent an endoscopic procedure between June 1, 2010 and July 15, 2017. Eosinophilic peak counts in 1 HPF were obtained by a medical student and an experienced gastrointestinal pathologist. RESULTS: Eosinophilic peak counts in suspected EoE patients are highly variable (esophagus : IQR 66-178, median 110 ; stomach : IQR 2-10, median 3 ; duodenum : IQR 16-44, median 25). No significant correlation was found between eosinophilic peak counts at different biopsy locations. The inter-observer and intra-observer correlation for reporting eosinophilic peak counts was in the nearperfect range (ρ ranged from 0.93 to 0.99, P<0.0001). CONCLUSIONS: Our data suggest that the accuracy of determining eosinophilic peak counts is not influenced by the pathologist's experience. Therefore, variability in reporting eosinophilic peak counts is unlikely to influence the diagnostic accuracy of EoE. To further improve diagnostic accuracy, investigation of other histologic features observed in EoE is needed.

Prognostic value of the circumferential resection margin and its definitions in esophageal cancer patients after neoadjuvant chemoradiotherapy.

The accepted importance of a positive circumferential resection margin (CRM) (defined as R1 in the TNM classification) is based on histopathology of the resection specimen obtained after primary surgery in esophageal cancer patients. The aim of this study is to look for the prognostic value of CRM after neoadjuvant chemoradiotherapy and to compare the clinical significance of a histologically CRM < 1 mm from the cut margin (Royal College of Pathologists definition of R1) to a positive cut margin (College of American Pathologists definition of R1) and to ≥1 mm margin (R0) resections in patients with ypT3-esophageal tumors after neoadjuvant chemoradiotherapy. Between 2000 and 2014, 458 patients who received esophagectomy after neoadjuvant chemoradiation therapy were selected. Overall (OS) and disease-free survival (DFS) were calculated by means of Kaplan-Meier curves and compared by Cox regression analysis. There were 163 (35.9%) patients who had a ypT3 tumor; in 118 (72.4%) resection was complete (R0). In 37 (22.7%) patients a CRM < 1 mm was found and 8 (4.9%) had a circumferential R1-resection. CRM involvement was inversely correlated with tumor regression grading, lymph node capsular involvement, and number of positive lymph nodes. On univariate analysis, no statistically significant difference was found between R0-resection and CRM < 1 mm (P = 0.103) for OS, but DFS showed a significant difference (P = 0.025). Circumferential R1-resections showed a significant difference compared to R0-resections for OS and DFS (both P = 0.002). In multivariate analysis, extracapsular lymph node involvement and circumferential R1-resection were withheld as independent prognosticators for OS, whereas extracapsular lymph node involvement, absence of regression on the primary tumor and circumferential R1-resection were withheld for DFS. After correcting for different variables in the multivariate model, CRM < 1 mm showed no statistical difference compared to R0-resections neither for OS nor for DFS. After neoadjuvant chemoradiotherapy, CRM is correlated with biological behavior of the tumor and with therapy response. Furthermore it is an independent prognosticator for OS and DFS. However CRM < 1 mm itself is no independent prognosticator for OS nor DFS survival in multivariable analysis. These results suggest that the definition of R1-resection should be limited to true invasion of the section plane.

Oesophageal biopsies are insufficient to predict final histology after endoscopic resection in early Barrett's neoplasia.

BACKGROUND: Endoscopic resection (ER) with or without ablation is the first choice treatment for early Barrett's neoplasia. Adequate staging is important to assure a good oncological outcome. OBJECTIVE: The purpose of this study was to investigate the diagnostic accuracy of pre-operative biopsies in patients who undergo ER for high-grade dysplasia (HGD) or early adenocarcinoma (EAC) in Barrett's oesophagus (BE) and the cardia. METHODS: Between November 2005-May 2012, 142 ERs performed in 137 patients were obtained. Worst pre-ER and ER histology were compared. Upgrading/downgrading was defined as any more/less severe histological grading on the ER specimen. RESULTS: The accuracy of pre-ER biopsies in predicting final histology was 61%. ER changed the pre-treatment diagnosis in 55 of the 142 procedures (39%) with downgrading in 23 cases (16%) and upgrading from HGD to T1a or T1b in 32 cases (23%). In the majority of upgraded cases, a visible lesion according to the Paris classification could be detected (26/32, 81%). CONCLUSION: The diagnostic accuracy of oesophageal biopsies alone in predicting final pathology in Barrett's dysplasia is only 61%. The majority of upgraded lesions are detectable. When ablative therapy is considered in HGD Barrett's dysplasia a meticulous inspection for and removal of all small visible lesions is mandatory.

Neoadjuvant chemoradiation treatment followed by surgery for esophageal cancer: there is much more than the mandard tumor regression score.

OBJECTIVE: Tumor regression grading (TRG) systems categorize residual tumor volume on the primary tumor after neoadjuvant treatment. Aim was to evaluate the impact of Mandard TRG, residual tumor depth (ypT) and residual lymph node status (ypN) and extent (ELNI) i.e. intracapsular versus extracapsular involvement on overall (OS) and disease-free survival (DFS) in esophageal carcinoma. METHODS: Between 2005 and 2014, 344 patients receiving R0-esophagectomy after neoadjuvant chemoradiation therapy (nCRT) were selected. Mandard TRG, ypTN and ELNI were prospectively recorded. RESULTS: Mandard TRG1 was found in 110 (32%); TRG2 in 120 (35%); TRG3 in 53 (15%); TRG4 in 54 (16%) and TRG5 in 7 (2%) patients. Both OS and DFS showed no significant difference between TRG1 and 2 (p = 0.059 and 0.105, respectively). Therefore, TRG1/2 was classified together as 'major response', TRG3/4 as 'minor response' and TRG5 as 'no response'. Multivariate analysis showed two independent prognosticators for OS (tumor regression response (TRR) and number of positive lymph nodes) and three independent prognosticators for DFS (TRR, ypT and ELNI). CONCLUSION: After nCRT followed by surgery for esophageal carcinoma, number of residual positive lymph nodes as well as TRR are prognosticators for OS. Minor TRR, ypT and extracapsular lymph node invasion are prognosticators for recurrence.

The Leuven Immunomodulatory Protocol Promotes T-Regulatory Cells and Substantially Prolongs Survival After First Intestinal Transplantation.

Intestinal transplantation (ITx) remains challenged by frequent/severe rejections and immunosuppression-related complications (infections/malignancies/drug toxicity). We developed the Leuven Immunomodulatory Protocol (LIP) in the lab and translated it to the clinics. LIP consists of experimentally proven maneuvers, destined to promote T-regulatory (Tregs)-dependent graft-protective mechanisms: donor-specific blood transfusion (DSBT); avoiding high-dose steroids/calcineurin-inhibitors; and minimizing reperfusion injury and endotoxin translocation. LIP was tested in 13 consecutive ITx from deceased donors (2000-2014) (observational cohort study). Recipient age was 37 years (2.8-57 years). Five-year graft/patient survival was 92%. One patient died at 9 months due to aspergillosis, another at 12 years due to nonsteroidal anti-inflammatory drug-induced enteropathy. Early acute rejection (AR) developed in two (15%); late AR in three (23%); all were reversible. No chronic rejection (CR) occurred. No malignancies developed and estimated glomerular filtration rate remained stable post-Tx. At last follow-up (3.5 years [0.5-12.5 years]), no donor-specific antibodies were detected and 11 survivors were total parenteral nutrition free with a Karnofsky score >90% in 8 recipients (follow-up >1 years). A high frequency of circulating CD4+ CD45RA- Foxp3hi memory Tregs was found (1.8% [1.39-2.21]), comparable to tolerant kidney transplant (KTx) recipients and superior to stable immunosuppression (IS)-KTx, KTx with CR, and healthy volunteers. In this ITx cohort we show that DSBT in a low-inflammatory/pro-regulatory environment activates Tregs at levels similar to tolerant-KTx, without causing sensitization. LIP limits rejection under reduced IS and thereby prolongs long-term survival to an extent not previously attained after ITx.

KRAS, NRAS, BRAF mutation comparison of endoscopic and surgically removed primary CRC paired samples: is endoscopy biopsy material adequate for molecular evaluation?

BACKGROUND: An everyday clinical practice dilemma in the 20-30% of metastatic colorectal cancer (CRC) patients that have not been operated on their primary tumour, is, under which specific histopathology and molecular circumstances, an endoscopic biopsy could be considered adequate to provide a representative RAS/BRAF molecular status to guide treatment. METHODS: A consecutive series of 193 paired biopsy and primary CRC tumour samples between August 2008 and 2010 available in the Department of Pathology archives, University Hospitals, KU Leuven were retrieved. For a pair to be included, in the endoscopic biopsy, 20% of invasive adenocarcinoma cells should be present and enough slides to yield an extracted DNA concentration of ⩾5 ng µl(-1), and no <2 ng µl(-1) should be available for cutting. Exons 2-4 KRAS/NRAS, BRAF, PIK3CA molecular evaluation was performed with RT-PCR and Sequenom. RESULTS: From 165 deemed adequate by the pathologist pairs, 85 (51.5%) were concordantly mutated in at least one of the tested genes, 70 (42.5%) were wt and 10 (6%) were discordant, harbouring a mutation in the primary and not in the endoscopic biopsy. In the re-evaluation, when more slides were cut per discordant pair, mutational status changed in two of the six discordantly KRAS-mutated pairs. A strong strength of agreement for both runs was observed (Cohen's kappa, k=0.877, P<0.001 and k=0.901, P<0.001, respectively) between the surgically acquired and the endoscopic biopsy specimens' evaluation. CONCLUSIONS: Based on our results, an endoscopic biopsy could provide an accurate mutational profile and become a justified alternative to a surgically removed primary tumour specimen, as long as specific histopathology criteria are met.

Skin as marker for collagen type I/III ratio in abdominal wall fascia.

PURPOSE: An altered collagen metabolism could play an important role in hernia development. This study compared collagen type I/III ratio and organisation between hernia and control patients, and analysed the correlation in collagen type I/III ratio between skin and abdominal wall fascia. METHODS: Collagen organisation was analysed in Haematoxylin-Eosin sections of anterior rectus sheath fascia, and collagen type I/III ratio, by crosspolarisation microscopy, in Sirius-Red sections of skin and anterior rectus sheath fascia, of 19 control, 10 primary inguinal, 10 recurrent inguinal, 13 primary incisional and 8 recurrent incisional hernia patients. RESULTS: Compared to control patients [7.2 (IQR = 6.8-7.7) and 7.2 (IQR = 5.8-7.9)], collagen type I/III ratio was significantly lower in skin and anterior rectus sheath fascia of primary inguinal [5.2 (IQR = 3.8-6.3) and 4.2 (IQR = 3.8-4.7)], recurrent inguinal [3.2 (IQR = 3.1-3.6) and 3.3 (IQR = 3-3.7)], primary incisional [3.5 (IQR = 3-3.9) and 3.4 (IQR = 3.3-3.6)] and recurrent incisional hernia [3.2 (IQR = 3.1-3.9) and 3.2 (IQR = 2.9-3.2)] patients; also incisional and recurrent inguinal hernia had lower ratio than primary inguinal hernia patients. Furthermore, collagen type I/III ratio was significantly correlated (r = 0.81; P < 0.001) between skin and anterior rectus sheath fascia. Finally, collagen organisation was comparable between hernia and control patients. CONCLUSIONS: Furthermore, in both skin and abdominal wall fascia of hernia patients, collagen type I/III ratio was lower compared to control patients, with more pronounced abnormalities in incisional and recurrent inguinal hernia patients. Importantly, collagen type I/III ratio in skin was representative for that in abdominal wall fascia.

Combined kidney and intestinal transplantation in patients with enteric hyperoxaluria secondary to short bowel syndrome.

Kidney transplantation is the treatment of choice for end-stage renal disease whereas indications for intestinal transplantation are currently restricted to patients with irreversible small bowel failure and severe complications of total parenteral nutrition (mostly shortage and infection of venous accesses, major electrolyte disturbances and liver failure). Enteric hyperoxaluria is secondary to certain intestinal diseases like intestinal resections, chronic inflammatory bowel disease and other malabsorption syndromes and can lead to end-stage renal disease requiring kidney transplantation. We report two patients suffering from renal failure due to enteric hyperoxaluria (secondary to extensive intestinal resection) in whom we elected to replace not only the kidney but also the intestine to prevent recurrence of hyperoxaluria in the transplanted kidney.

Recurrence pattern in patients with a pathologically complete response after neoadjuvant chemoradiotherapy and surgery for oesophageal cancer.

BACKGROUND: Little is known about recurrence patterns in patients with a pathologically complete response (pCR) or an incomplete response after neoadjuvant chemoradiotherapy (CRT) followed by resection for oesophageal cancer. This study was performed to determine the pattern of recurrence in patients with a pCR after neoadjuvant CRT followed by surgery. METHODS: All patients who received neoadjuvant CRT followed by oesophagectomy between 1993 and 2009 were identified from a database, and categorized according to pathological tumour response. Recurrences were classified as locoregional or distant. RESULTS: One hundred and eighty-eight patients were included. Median potential follow-up was 71·6 months. A pCR was achieved in 62 (33·0 per cent) of 188 patients. Recurrence developed in 24 (39 per cent) of 62 patients with a pCR and 70 (55·6 per cent) of 126 without a pCR (P = 0·044). Locoregional recurrence with or without synchronous distant metastases occurred in eight patients (13 per cent) in the pCR group and 31 (24·6 per cent) in the non-pCR group (P = 0·095). Locoregional recurrences without synchronous distant metastases occurred four (6 per cent) and ten (7·9 per cent) patients respectively (P = 0·945). The overall 5-year survival rate was significantly higher in the pCR group than in the non-pCR group (52 versus 33·9 per cent respectively; P = 0·019). CONCLUSION: Of patients with a pCR, 13 per cent still developed a locoregional recurrence. Although pCR is more favourable for survival, it is not synonymous with cure or complete locoregional disease control.

Analysis of HER2 expression and gene amplification in adenocarcinoma of the stomach and the gastro-oesophageal junction: rationale for the Belgian way of working.

The Human Epidermal growth factor Receptor 2 (HER2) has been established as a key player in the development of certain human tumors. ToGA trial has demonstrated that the addition of the monoclonal antibody blocking HER2 receptor, trastuzumab (Herceptin®), to chemotherapy significantly improves overall survival of patients with HER2-positive advanced or metastatic adenocarcinoma of the stomach or gastro-oesophageal junction. Therefore, it is essential that pathologists guarantee an accurate testing of HER2 status in these tumours. Following the international recommendations and the Belgian criteria for reimbursement of trastuzumab, a consortium of expert pathologists (Belgian Working Group Molecular Pathology) proposes an adaptation of the international guidelines in order to develop strategies for optimal performance, interpretation and reporting assays.

Effects of haptoglobin polymorphisms and deficiency on susceptibility to inflammatory bowel disease and on severity of murine colitis.

BACKGROUND: Haptoglobin (Hp) is a haemoglobin-binding protein with immunomodulatory properties. Its gene (16q22) harbours a common polymorphism with two different alleles: Hp1 and Hp2. Genotype Hp22 has been shown to be over-represented in different immune diseases. Results in Crohn's disease (CD) are contradictory. AIMS: To determine whether Hp plays a role in inflammatory bowel disease, both genetically and functionally. METHODS: 1061 patients with CD, 755 with ulcerative colitis (UC) and 152 with primary sclerosing cholangitis, as well as 452 healthy controls, were genotyped using touch-down PCR. To confirm association results, 464 CD trios and 151 UC trios were genotyped. Serum Hp concentrations were determined in 62 individuals of different genotype. Colitis was induced in mice with dextran sulphate sodium (DSS) and oxazolone (Oxa). Cytokine production was evaluated by mRNA quantification in colonic tissue and ELISA on supernatants of mesenteric lymph node cells. RESULTS: Prevalence of Hp2 was higher in CD and UC than in controls. In the confirmatory cohorts, Hp2 was over-transmitted to the affected offspring. Serum Hp concentrations were higher in individuals with genotypes Hp11 and Hp21 than in those with Hp22 (1.38 vs 0.89 g/l). DSS- and Oxa-induced colitis were more severe in Hp-deficient mice than in control mice and accompanied by higher concentrations (although not statistically significantly different) of tissue mRNA for cytokines. Interleukin-17 production was significantly higher in the presence of Hp-deficient serum compared with wild-type serum. CONCLUSIONS: The Hp gene may play a role in susceptibility to inflammatory bowel disease. Its implication in other immune diseases underscores the common pathways between these diseases. Experimental models of colitis showed that Hp has a protective role in inflammatory colitis, most likely by inhibiting the production of Th1 and Th17 cytokines.

FISH analysis of Lactobacillus biofilms in the gastrointestinal tract of different hosts.

AIMS: To investigate the spatial organization of endogenous and exogenously applied Lactobacillus communities at specific locations in the adult gastrointestinal tract of different hosts. METHODS AND RESULTS: Samples of the human, murine and avian gastrointestinal tract of subjects that received or not received a Lactobacillus probiotic were analysed by fluorescence in situ hybridization (FISH) with rRNA-targeted probes. High levels of endogenous lactobacilli were observed on the nonsecretory, stratified squamous epithelia present in the forestomach of mice and crop of chickens, respectively. These epithelial associations showed characteristics of bacterial biofilms, i.e. bacteria attached to a surface and embedded in a matrix of extracellular polymeric substances. In other regions of the analysed intestines, lactobacilli seemed to occur mainly as dispersed bacterial cells or as microcolonies. Exogenous administration of a Lactobacillus probiotic did increase the levels of loosely adherent Lactobacillus cells detected. However, the probiotic strains were unable to establish themselves inside the gastrointestinal biofilms. CONCLUSIONS: Gastrointestinal biofilms of lactobacilli occur only in specific niches in certain hosts, such as the murine forestomach and avian crop. SIGNIFICANCE AND IMPACT OF THE STUDY: Biofilm formation by lactobacilli in specific parts of animal gastrointestinal tracts was documented for the first time by FISH.