The abundance of a number of VOCs in feces differs markedly between Crohn's disease and other gastrointestinal conditions. Following treatment, the VOC profile is altered to more closely resemble that of healthy volunteers.
Microbial translocation is defined as the passage of viable microbes from the gastrointestinal (GI) tract to extraintestinal sites, such as the mesenteric lymph node (MLN), spleen, liver, kidneys, and blood. The ability of orally administered viable Saccharomyces boulardii to inhibit Candida albicans translocation from the GI tract was tested in antibiotic-decontaminated, specific pathogen-free (SPF) mice, which were orally challenged with C. albicans to promote intestinal overgrowth and subsequent translocation of this organism. Oral S. boulardii treatment reduced the incidence of MLN cultures positive for C. albicans but did not decrease the numbers of C. albicans per gram of MLN in these immunocompetent mice. Prednisolone immunosuppression increased translocation of C. albicans to the MLN and allowed translocating C. albicans to spread systemically to the spleen, liver, and kidneys. In these immunosuppressed mice, orally administered S. boulardii decreased both the incidence of C. albicans translocation to the MLN, liver, and kidneys and the number of translocating C. albicans per gram of MLN, spleen, and kidneys.
The relative abundance of different groups of sulphate-reducing bacteria (SRB) in faecal DNA collected before and after therapy from patients suffering from Crohn's disease (CD), irritable bowel syndrome (IBS) or ulcerative colitis (UC) has been compared with that from healthy controls. Growth tests revealed that SRB were not more abundant in samples from patients with CD before treatment than in the healthy control group. For most of the 128 samples available, these preliminary results were confirmed using degenerate PCR primers that amplify the dsrAB gene. However, some samples from patients with CD before treatment contained a growth inhibitor that was absent from IBS or UC samples. In-depth sequencing of PCR-generated dsrB fragments revealed that the diversity detected was surprisingly low, with only eight strains of SRB and the sulphite-reducing bacterium, Bilophila wadsworthia, detected above the 0.1% threshold. The proportion of the two major species detected, B. wadsworthia and Desulfovibrio piger, was as high as 93.5% of the total SRB population in the healthy control group and lower in all patient groups. Four previously undescribed species were found: it is impossible to predict whether they are sulphate or sulphite-reducing bacteria.
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