Fecal microbiota transplants from patients with irritable bowel syndrome and anxiety alter gut function and behavior in germ-free mice.

There are few validation studies of existing diagnostic criteria for irritable bowel syndrome (IBS). We conducted a validation study of the Rome and Manning criteria in secondary care. We collected complete symptom, colonoscopy, and histology data from 1848 consecutive adult patients with gastrointestinal symptoms at 2 hospitals in Hamilton, Ontario; the subjects then underwent colonoscopy. Assessors were blinded to symptom status. Individuals with normal colonoscopy and histopathology results, and no evidence of celiac disease, were classified as having no organic gastrointestinal disease. The reference standard used to define the presence of true IBS was lower abdominal pain or discomfort in association with a change in bowel habit and no organic gastrointestinal disease. Sensitivity, specificity, and positive and negative likelihood ratios, with 95% confidence intervals, were calculated for each diagnostic criteria. In identifying patients with IBS, sensitivities of the criteria ranged from 61.9% (Manning) to 95.8% (Rome I), and specificities from 70.6% (Rome I) to 81.8% (Manning). Positive likelihood ratios ranged from 3.19 (Rome II) to 3.39 (Manning), and negative likelihood ratios from 0.06 (Rome I) to 0.47 (Manning). The level of agreement between diagnostic criteria was greatest for Rome I and Rome II (κ = 0.95), and lowest for Manning and Rome III (κ = 0.59). Existing diagnostic criteria perform modestly in distinguishing IBS from organic disease. There appears to be little difference in terms of accuracy. More accurate ways of diagnosing IBS, avoiding the need for investigation, are required.

The gut microbiota has been implicated in chronic pain disorders, including irritable bowel syndrome (IBS), yet specific pathophysiological mechanisms remain unclear. We showed that decreasing intake of fermentable carbohydrates improved abdominal pain in patients with IBS, and this was accompanied by changes in the gut microbiota and decreased urinary histamine concentrations. Here, we used germ-free mice colonized with fecal microbiota from patients with IBS to investigate the role of gut bacteria and the neuroactive mediator histamine in visceral hypersensitivity. Germ-free mice colonized with the fecal microbiota of patients with IBS who had high but not low urinary histamine developed visceral hyperalgesia and mast cell activation. When these mice were fed a diet with reduced fermentable carbohydrates, the animals showed a decrease in visceral hypersensitivity and mast cell accumulation in the colon. We observed that the fecal microbiota from patients with IBS with high but not low urinary histamine produced large amounts of histamine in vitro. We identified Klebsiella aerogenes , carrying a histidine decarboxylase gene variant, as a major producer of this histamine. This bacterial strain was highly abundant in the fecal microbiota of three independent cohorts of patients with IBS compared with healthy individuals. Pharmacological blockade of the histamine 4 receptor in vivo inhibited visceral hypersensitivity and decreased mast cell accumulation in the colon of germ-free mice colonized with the high histamine-producing IBS fecal microbiota. These results suggest that therapeutic strategies directed against bacterial histamine could help treat visceral hyperalgesia in a subset of patients with IBS with chronic abdominal pain.

Anxiety and depression occur frequently in patients with functional gastrointestinal disorders (FGIDs), but their precise prevalence is unknown. We addressed this issue in a large cohort of adult patients and determined the underlying factors. In total, 4,217 new outpatients attending 2 hospitals in Hamilton, Ontario, Canada completed questionnaires evaluating FGIDs and anxiety and depression (Hospital Anxiety and Depression scale). Chart review was performed in a random sample of 2,400 patients. Seventy-six percent of patients fulfilled Rome III criteria for FGIDs, but only 57% were diagnosed with FGIDs after excluding organic diseases, and the latter group was considered for the analysis. Compared with patients not meeting the criteria, prevalence of anxiety (odds ratio (OR) 2.66, 95% confidence interval (CI): 1.62–4.37) or depression (OR 2.04, 95% CI: 1.03–4.02) was increased in patients with FGIDs. The risk was comparable to patients with organic disease (anxiety: OR 2.12, 95% CI: 1.24–3.61; depression: OR 2.48, 95% CI: 1.21–5.09). The lowest prevalence was observed in asymptomatic patients (OR 1.37; 95% CI 0.58–3.23 and 0.51; 95% CI 0.10–2.48; for both conditions, respectively). The prevalence of anxiety and depression increased in a stepwise manner with the number of co-existing FGIDs and frequency and/or severity of gastrointestinal (GI) symptoms. Psychiatric comorbidity was more common in females with FGIDs compared with males (anxiety OR 1.73; 95% CI 1.35–2.28; depression OR 1.52; 95% CI 1.04–2.21). Anxiety and depression were formally diagnosed by the consulting physician in only 22% and 9% of patients, respectively. Psychiatric comorbidity is common in patients referred to a secondary care center but is often unrecognized. The prevalence of both anxiety and depression is influenced by gender, presence of organic diseases, and FGIDs, and it increases with the number of coexistent FGIDs and frequency and severity of GI symptoms.

Background. Alterations in the intestinal microbiota, characterized by depletion of anti-inflammatory bacteria, such as Firmicutes, in patients with ulcerative