Background: Colorectal cancer is the second commonest cause of cancer mortality.Some countries are implementing colorectal cancer screening to detect lesions at an early stage using non-invasive tools like the faecal immunochemical test. Despite affordability, this test shows a low sensitivity for precancerous lesions and a low positive predictive value for colorectal cancer, resulting in a high false-positive rate.Aim: To develop a new, non-invasive colorectal cancer screening tool based on bacterial faecal biomarkers, which in combination with the faecal immunochemical test, could allow a reduction in the false-positive rate. This tool is called risk assessment of intestinal disease for colorectal cancer (RAID-CRC). Methods:We performed both the faecal immunochemical test and the bacterial markers analysis (RAID-CRC test) in stool samples from individuals with normal colonoscopy (167), non-advanced adenomas (88), advanced adenomas (30) and colorectal cancer (48). All the participants showed colorectal cancer-associated symptoms.Results: Performance of the faecal immunochemical test for advanced neoplasia (ie advanced adenoma and colorectal cancer) was determined by using the cut-off value established in Catalonia (20 µg haemoglobin/g of faeces) for a population-based screening approach. Sensitivity and specificity values of 83% and 80%, respectively, and positive and negative predictive values of 56% and 94%, respectively, were obtained. When both the immunological and the biological analysis were combined, the corresponding values were 80% and 90% for sensitivity and specificity, respectively, and 70% and 94% for positive and negative predictive values, respectively, resulting in a 50% reduction of the false-positive rate.Conclusions: RAID-CRC test allows a substantial reduction in the faecal immunochemical test false-positive results (50%) in a symptomatic population. Further validation is indicated in a colorectal cancer-screening scenario. | 1411MALAGÓN et AL.

Background and Aims Crohn’s disease and ulcerative colitis evolve with alternate outbreaks and remissions of variable duration in both cases. Despite the advances, about 10-30% of patients do not respond to the treatment after the induction period. Besides, between 20% to 50% further patients need an optimization of the dose to respond the treatment. Recent studies have pointed gut microbiota can play a role in the anti-TNF treatment response. This study aimed to define a bacterial signature that could be used to predict the response of patients to anti-TNF treatment. Methods There were obtained 38 stool samples from 38 IBD patients before starting anti-TNF treatments: Adalimumab, Golimumab or Infliximab. Patients were differentiated in 2 groups: responders and non-responders to biological treatment. From each sample, DNA was purified and used in a qPCR for the quantification of the 8 microbial markers. Results In this proof of concept, the predictive ability to identify anti-TNF treatment responders was analyzed. An algorithm consisting in the combination of 4 bacterial markers showed a high capacity to discriminate between responders and non- responders. The algorithm proved high sensitivity and specificity reporting values of 93.33% and 100% respectively, with a positive predictive value of 100% and a negative predictive value of 75% for predicting response to biologic treatment. Conclusions A specific bacterial signature could beneficiate patients with inflammatory bowel disease predicting the therapeutic effectiveness of an anti-TNF treatment, leading to a personalized therapy, improving the patients’ quality of life, saving costs and gaining time in patient improvement.

Guidelines recommend routine screening for colorectal cancer (CRC) in asymptomatic adults starting at age 50. The most extensively used noninvasive test for CRC screening is the fecal immunochemical test (FIT), which has an overall sensitivity for CRC of approximately 61.0%-91.0%, which drops to 27.0%-67.0% for advanced adenomas. These figures contain a high false-positive rate and a low positive predictive value. This work aimed to develop a new, noninvasive CRC screening tool based on fecal bacterial markers capable of decreasing FIT false-positive rates in a FIT-positive population. We defined a fecal bacterial signature (RAID-CRC Screen) in a proof-of-concept with 172 FIT-positive individuals and validated the obtained results on an external cohort of 327 FIT-positive subjects. All study participants had joined the national CRC screening program. In the clinical validation of RAID-CRC Screen, a sensitivity of 83.9% and a specificity of 16.3% were obtained for the detection of advanced neoplasm lesions (advanced adenomas and/or CRC). FIT 20 μg/g produced 184 false-positive results. Using RAID-CRC Screen, this value was reduced to 154, thus reducing the false-positive rate by 16.3%. The RAID-CRC Screen test could be implemented in CRC screening programs to allow a significant reduction in the number of colonoscopies performed unnecessarily for FIT-positive participants of CRC screening programs.

Inflammatory bowel disease (IBD), including its two main categories (Crohn's disease and ulcerative colitis), has been linked both to gut microbiota and to diet. Bread is a daily food that has a potential capacity as a prebiotic. Our aim was to evaluate different bread-making processes and their effect on fecal colonic microbiota in IBD patients. The microbial composition of several sourdoughs and dough samples was analyzed by high-throughput sequencing of 16S and 18S rRNA genes. Three types of bread, which followed different bread-making processes, were in vitro digested and incubated with feces from IBD patients. Changes in gut microbiota were assessed by a quantitative polymerase chain reaction using specific bacterial sequence targets. Short-chain fatty acid production was also analyzed by gas chromatography. Lactobacillus sanfranciscensis was the dominant lactic acid bacteria species found in sourdough and bread doughs prepared using sourdough, whereas Saccharomyces cerevisiae was the most dominant yeast in all groups, especially in bread doughs before baking. Differences in microbial composition in raw bread doughs were more related to the type of dough and elaboration than to fermentation time lengths. The analysis of in vitro fecal incubations with bread conditions revealed an increase in most bacterial groups analyzed and short-chain fatty acid production, both in Crohn's disease and ulcerative colitis samples. Most remarkable increases in short-chain fatty acid production mirrored higher abundances of Roseburia species. The potential prebiotic properties observed were mainly obtained when using a high quantity of bread, regardless of bread type. Overall, this study highlights the bacterial dynamics within the bread-making process and the potential prebiotic effect in IBD patients.

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) patients have different faecal microbiota profiles compared to healthy controls. Prebiotics intake influences intestinal microbiota composition which in turn influence the growth of short-chain fatty acids (SCFA) producing bacteria. This study aimed to evaluate the capacity of Previpect, a new prebiotic obtained from grapes fibre, to balance the dysbiosis found in patients with intestinal disorders. This was achieved through the analysis of specific bacterial markers and SCFA production using an in vitro fermentation system and comparing the obtained results with those obtained with other commercial prebiotics. Fresh faecal samples from patients with IBD (N = 6), IBS (N = 3), and control subjects (N = 6) were used. Previpect showed high fermentative ability enabling the growth of butyrate producing bacteria and increasing SCFA concentration up to 2.5-fold. Previpect is a promising prebiotic which may be used as a therapeutic strategy towards promotion of intestinal microbiota restoration, microbial healing, and as a preventive supplement for healthy individuals.

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Background Dysbiosis is a widely used but unspecific term. It has been defined as any change in the composition of resident microbial communities relative to the ones found in healthy individuals. But it is still unclear which are the appropriate communities to define it and the reference values to measure it. Different studies have described dysbiosis in various diseases such as Inflammatory Bowel Disease (IBD), diabetes, rheumatoid arthritis, and autism, among others. Besides, the microbiota can be altered by transient factors such as antibiotics, diet, stress, or infections. Therefore, different degrees of severity can be associated with the term dysbiosis from which pathological and transient dysbiosis can be differentiated. This work aimed at defining more specifically the term intestinal dysbiosis and to differentiate both transient and pathological dysbiosis. Methods Fifteen key microbial markers belonging to the principal families, classes and orders found in the human intestinal microbiota were accurately selected based on its functionality: F. prausnitzii (Fpra), E. coli (Eco), Firmicutes (Fir), Bacteroidetes (Bac), A. muciniphila (Akk), Ruminococcus sp. (Rum), Roseburia sp. (Ros), Gammaproteobacteria (Gam), Clostridia cluster I (Clo), Clostridia cluster XIV (XIV), Enterococcus sp., Lactobacillus sp. (Lac), C. albicans (Can), M. smithii (Msm), and the total bacterial load (Eub). The dysbiosis was defined using stool samples in a cohort of healthy subjects (n=24) and then validated with 9 patients diagnosed with intestinal diseases 4 IBD and 2 Irritable Bowel Syndrome (IBS)). Total DNA was extracted and the abundance of microbial markers was analysed by qPCR. Together with the establishment of the most common range in which each microbial marker was found, an index to define the pathological dysbiosis was calculated. Results Almost all healthy subjects analysed presented one or two slightly altered markers. The affected microbial markers in this “transient dysbiosis” were Fpra, Akk, and Ros, which are indicative of the mucous layer state, Firm as indicative of the lifestyle and fiber intake, Gam as characteristic of the pro-inflammatory state of the gut, and Msm as an altered intestinal habit and gas production. All patients analyzed (IBD and IBS) presented alterations mainly of the bacteria inhabiting the mucosa and an alteration of the opportunistic species related to the disrupted mucous layer and defining “pathological dysbiosis”. Conclusion This study establishes an appropriate abundance range of key microbial markers in the gut, leading to a specific definition of dysbiosis which allows to differentiate the pathological from the transient dysbiosis. These results need further validation in a larger patient cohort.

Background Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS) are two intestinal disorders with unknown aetiology. IBD presents two main forms which are Crohn’s disease (CD) and ulcerative colitis (UC). It has been reported recently that bacterial communities present in the colon of patients with either IBD or IBS are structurally different compared to those found in healthy individuals. This dysbiosis mainly consists of a decrease of butyrate producing bacteria and, therefore, the recovery of this metabolic group should be at the baseline of any successful treatment. The main goal of this proof-of-concept study was to test the capacity of a new prebiotic of selected dietary fibre obtained from grape to balance the dysbiosis found in patients with different intestinal disorders. Methods In this study, fresh faecal samples from 6 healthy subjects, 3 CD, 3 UC, and 3 IBS were collected at the Hospital Universitari Dr. Josep Trueta. Fresh samples were diluted 1:5 with fermentation buffer and incubated with 200 mg of prebiotic at 37 ºC under agitation for 72 h. Results were compared with those obtained with various commercial prebiotics after simulating in vitro digestion: inulin, grape pectin, and grape seed extract (GSPE). Total DNA was extracted and the abundance of butyrate-producing bacterial markers: F. prausnitzii (Fpra), its two phylogroups (PHGI and PHGII), Roseburia spp. (Ros) and S. variabile (Sva) was analysed by qPCR. Bacterial activity was determined by measuring short chain fatty acids (SCFA) concentration (butyrate, acetate, and propionate) by gas chromatography. Results The abundance of all butyrate-producing bacteria analysed increased after incubation with the new prebiotic. Among them, Ros presented significantly higher abundance values with respect to negative control in healthy, CU, and IBS patients. It also showed a significant increase in all individuals analysed compared to inulin, grape pectin, and GSPE. Fermentation of the tested new prebiotic, produced significantly higher concentrations of SCFA (p < 0.001) when compared to negative control and all other commercial fibres. Acetate concentration was a 241% higher than negative control, followed by butyrate (187%), and propionate (169%). Conclusion The studied prebiotic produces in vitro an increase of the abundance and enhancement of the metabolism of butyrate-producing bacteria, when compared to commercial prebiotics. These results suggest that this new fibre is a promising prebiotic to be used in promotion of intestinal microbiota restoration at mucosa.