Brain-gut-axis-IBS and HC-metagenomic faecal samples. Brain-gut-axis-IBS and HC

63 female patients with IBS, mean age 32 years (range, 19-57 years), meeting Rome III criteria with mostly moderate to severe IBS were recruited from the Gastroenterology Department, University Hospital, Linköping, Sweden. 34 healthy age-matched female controls (HC), mean age 33 years (range, 20-55 years), without medical history of gastrointestinal symptoms or complaints, were recruited by advertisement. IBS patients were classified according to predominant bowel habit into IBS-mixed (IBS-M; n=36), IBS-constipation (IBS-C; n=12), and IBS-diarrhea (IBS-D; n=15). Exclusion criteria for both study groups were established via interviews with participants to determine if they suffered from any organic gastrointestinal disease, metabolic or neurological disorders, and severe psychiatric disease (e.g., schizophrenia, bi-polar disorder, psychosis, etc.), as well as factors known to affect gut barrier function, including self-reported allergy for those undergoing sigmoidoscopy, self-reported nicotine intake within the previous two months, and self-reported regular NSAID use. All participants were required to be fluent in Swedish. Whole-genome next-generation sequencing was done by GATC Biotech (Konstanz, Germany). After thawing each stool sample, they underwent cell wall lysis, DNA extraction and purification. DNA sequencing was performed using an Illumina Technology HiSeq 4000 (read mode 2 x 150bp). The sequence reads were then inspected for base quality from the 3´ and 5´ ends for removal of low-quality reads using a sliding window approach. Bases with average phred quality below 15 were considered of low quality, and only mate pairs (forward and reverse read) were used for the next analysis step.