Summary Background The faecal‐associated microbiota is commonly seen as a surrogate of the mucosal‐associated microbiota. However, previous studies indicate that they are different. Furthermore, analyses of the mucosal microbiota are commonly done after standard bowel cleansing, affecting the microbial composition. Aim To compare the mucosal‐associated microbiota, obtained from unprepared colon, with faecal‐associated microbiota in healthy subjects and irritable bowel syndrome (IBS) patients. Methods Faecal and mucosal biopsies were obtained from 33 IBS patients and 16 healthy controls. Of IBS patients, 49% belonged to the diarrhoea‐predominant subgroup and 80% suffered from IBS symptoms during at least 5 years. Biopsies were collected from unprepared sigmoid colon and faecal samples a day before colonoscopy. Microbiota analyses were performed with a phylogenetic microarray and redundancy discriminant analysis. Results The composition of the mucosal‐ and the faecal‐associated microbiota in unprepared sigmoid colon differs significantly (P = 0.002). Clinical characteristics of IBS did not correlate with this difference. Bacteroidetes dominate the mucosal‐associated microbiota. Firmicutes, Actinobacteria and Proteobacteria dominate the faecal‐associated microbiota. Healthy subjects had a significantly higher (P < 0.005) abundance (1.9%) of the bacterial group uncultured Clostridiales I in the mucosal‐associated microbiota than IBS patients (0.3%). Bacterial diversity was higher in faecal‐ compared with mucosal‐associated microbiota in IBS patients (P < 0.005). No differences were found in healthy subjects. Conclusions Differences in the mucosal‐associated microbiota between healthy individuals and IBS patients are minimal (one bacterial group) compared to differences in the faecal microbiota of both groups (53 bacterial groups). Microbial aberrations characterising IBS are more pronounced in the faeces than in the mucosa.

SUMMARY BackgroundA subset of irritable bowel syndrome (IBS) patients, denoted post-infectious IBS (PI-IBS), develop symptoms after an enteric infection. Bacterial dysbiosis and mucosal inflammation have been proposed to be involved in the pathophysiology of this entity.

BackgroundAnkylosing spondylitis (AS) shares many characteristics with inflammatory bowel disease (IBD). Intestinal microbiota most likely plays an important role in the development of IBDs and may also be involved in the pathogenesis of AS. We aimed to define and compare the fecal microbiota composition in patients with AS, ulcerative colitis (UC), and healthy controls (HC) and to determine relationships between fecal microbiota, fecal calprotectin, and disease-related variables in AS.MethodsFecal microbiota composition was assessed with GA-map™ Dysbiosis Test (Genetic Analysis, Oslo, Norway), which also reports the degree of deviation of the microbiota composition compared with a healthy control population, a Dysbiosis Index (DI) score 1–5. The AS patients were assessed with questionnaires, back mobility tests, fecal calprotectin, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).ResultsTotally, 150 patients with AS (55% men, median age 55.5 years, median BASDAI 3.2), 18 patients with UC (56% men, median age 30.5 years), and 17 HC (65% men, median age 22 years) were included. Principal component analysis showed highly separate clustering of fecal microbiota from the patients with AS, UC, and HC. Compared with HC, fecal microbiota in AS was characterized by a higher abundance of Proteobacteria, Enterobacteriaceae, Bacilli, Streptococcus species, and Actinobacteria, but lower abundance of Bacteroides and Lachnospiraceae.Further, fecal microbiota composition differed between patients with normal (≤ 50 mg/kg, n = 57) and increased (≥ 200 mg/kg, n = 36) fecal calprotectin. Patients with increased fecal calprotectin had lower abundance of bacteria with anti-inflammatory properties such as Faecalibacterium prausnitzii and Clostridium and higher abundance of the genus Streptococcus. No association was found between the fecal microbiota composition and HLAB27 status, disease activity, function, or medication. Dysbiosis (defined as DI ≥ 3) was found in 87% of AS patients.ConclusionsPatients with AS have a distinct fecal microbiota signature, which is linked to fecal calprotectin levels, a marker of intestinal inflammation, but not to other clinical parameters. These findings suggest a local interplay between intestinal microbiota and gut inflammation in AS.Trial registrationClinicalTrials.gov, NCT00858819. Registered March 9, 2009.

The pharmacokinetics of a single intravenous injection of 100 mg iron hydroxide–sucrose complex labelled with a tracer in the form of 52Fe/59Fe was followed in six anaemic patients for a period ranging from 6 to 8.3 h using positron emission tomography (PET). Red cell utilization of the labelled iron was followed for 4 weeks. PET data showed radioactive uptake by the liver, spleen and bone marrow. The uptake by the macrophage‐rich spleen demonstrated the reticuloendothelial uptake of this iron preparation, with subsequent effective release of that iron for marrow utilization. Red cell utilization, followed for 4 weeks, ranged from 59% to 97%. The bone marrow influx rate constant was independent of blood iron concentration, indicating non‐saturation of the transport system in bone marrow. This implied that higher doses of the iron complex can probably be used in the same setting. A higher influx rate into the marrow compared with the liver seemed to be consistent with higher red cell utilization. This would indicate that early distribution of the injected iron complex may predict the long‐term utilization.

Objectives Human milk oligosaccharides safely and beneficially impact bifidobacteria abundance in healthy adults, while their effects in patients with irritable bowel syndrome (IBS) are unknown. Hence, we aimed to determine the dose of 4:1 mix of 2’‐O‐fucosyllactose and Lacto‐N‐neotetraose (2’FL/LNnT) that increases fecal bifidobacteria abundance without aggravating overall gastrointestinal symptoms in IBS patients in a randomized, double‐blind, controlled study. Additionally, the impact of 2’FL/LNnT on the fecal bacterial profile was assessed. Methods Irritable bowel syndrome patients diagnosed according to the Rome IV criteria received placebo (glucose), or 5 g or 10 g 2’FL/LNnT for 4 weeks followed by a four‐week follow‐up period. Gastrointestinal Symptom Rating Scale‐IBS was used to assess gastrointestinal symptom severity; fecal microbiota composition was evaluated by GA‐map™ Dysbiosis Test. Results Of the included 60 patients, two (one placebo and one 10 g) discontinued prematurely. Fecal bifidobacteria abundance was increased at week 4, but not at week 8, in the 10 g group compared to the other groups. Severity of overall or individual gastrointestinal symptoms did not differ between the groups at week 4 or 8, and no symptom deterioration was seen in any of the groups. The 10 g dose influenced overall fecal microbiota composition, and responders—defined as bifidobacteria increase ≥50%—could be discriminated from non‐responders based on fecal microbiota modulation. Conclusions The 10 g dose of 2’FL/LNnT induced an increase in the beneficial Bifidobacterium spp. without aggravating gastrointestinal symptoms in patients with IBS. This approach may be worthwhile to modulate gut microbiota of IBS patients toward a healthier profile.