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A therapeutic goal for patients with ulcerative colitis (UC) is deep remission including clinical remission and mucosal healing. Mucosal healing was previously defined by endoscopic appearance, but recent studies demonstrate that histological improvements can minimize the risks of experiencing clinical relapse after achieving endoscopic remission, and there is growing interest in the value and feasibility of histological targets of treatment in inflammatory bowel disease, and specifically UC. In this review article, we identify remaining challenges and discuss an evolving role of histology in the management of UC.

Abstract Background Patients with inflammatory bowel disease (IBD) are at risk of developing dysplasia and, subsequently, colorectal cancer (CRC) owing to chronic inflammation. Patients may also experience other severe disease complications, such as hospitalization and surgery. Several biologics are available for the treatment of patients with IBD and some patients require multiple lines of treatment owing to loss of response or tolerability to their prescribed biologic. Previous studies suggest that the choice of initial biologic treatment may impact the outcomes of later treatment lines. In this study, we assessed adverse clinical outcomes in patients with Crohn’s disease (CD) or ulcerative colitis (UC) who received different biologic treatment sequences. Methods ROTARY part B was a retrospective cohort study using the Optum® Clinical Database that evaluated the incidences of IBD-related hospitalization, IBD-related surgery, dysplasia, CRC, and infections in patients with CD or UC who received two biologics successively. First-line biologics included adalimumab, infliximab, ustekinumab (CD only), and vedolizumab; second-line biologics included infliximab and adalimumab. Results In patients with CD, the treatment sequence of ustekinumab to infliximab was associated with the highest overall incidences of hospitalization (51.9%), surgery (40.7%), CRC (3.7%), and infection (37.0%). Vedolizumab followed by an anti-tumor necrosis factor alpha (anti-TNFα) treatment was associated with a significantly lower risk of experiencing an adverse medical event (hospitalization, surgery, or infection) than two successive anti-TNFα treatments (odds ratio, 1.526; 95% confidence interval, 1.004–2.320; P

Summary: Background: The Bowel Ultrasound Score (BUSS) accurately detects therapy-related changes by using the Simple Endoscopic Score for Crohn's disease (SES-CD) as the reference standard. We aimed to evaluate ultrasound remission as a treatment target and its prediction for long-term endoscopic remission. Methods: This single-centre prospective observational study, based at a tertiary referral centre in Milan, Italy, enrolled, between March 1, 2018, and January 31, 2021, adult patients with active CD (SES-CD >2) who were starting biologics. Colonoscopy and IUS was performed at baseline and at 12 months (mean 12.8 ± 4.2). The primary outcome was the predictive value of ultrasound remission at week 12 (BUSS ≤3.52) for long-term endoscopic remission at 12 months. The International Bowel Ultrasound Segmental Activity Score (IBUS-SAS) was also calculated and optimal cut-point to detect endoscopic remission was identified through ROC analysis. Findings: 93 patients with CD were included. Of these, 22 patients (24%) achieved endoscopic remission. Week 12 ultrasound remission predicted endoscopic remission (59% compared with 41% of the patients who were not in ultrasound remission; OR 9.93, 95% CI 3.10–31.80; p

Abstract Background There is a rapid increase in the incidence of inflammatory bowel diseases (IBD) in newly industrialized countries, yet epidemiological data is incomplete. We herein report the methodology adopted to study the incidence of IBD in newly industrialized countries and to evaluate the effect of environmental factors including diet on IBD development. Methods Global IBD Visualization of Epidemiology Studies in the 21st Century (GIVES-21) is a population-based cohort of newly diagnosed persons with Crohn’s disease and ulcerative colitis in Asia, Africa, and Latin America to be followed prospectively for 12 months. New cases were ascertained from multiple sources and were entered into a secured online system. Cases were confirmed using standard diagnostic criteria. In addition, endoscopy, pathology and pharmacy records from each local site were searched to ensure completeness of case capture. Validated environmental and dietary questionnaires were used to determine exposure in incident cases prior to diagnosis. Results Through November 2022, 106 hospitals from 24 regions (16 Asia; 6 Latin America; 2 Africa) have joined the GIVES-21 Consortium. To date, over 290 incident cases have been reported. All patients have demographic data, clinical disease characteristics, and disease course data including healthcare utilization, medication history and environmental and dietary exposures data collected. We have established a comprehensive platform and infrastructure required to examine disease incidence, risk factors and disease course of IBD in the real-world setting. Conclusions The GIVES-21 consortium offers a unique opportunity to investigate the epidemiology of IBD and explores new clinical research questions on the association between environmental and dietary factors and IBD development in newly industrialized countries.

Abstract Background Changes in microbial community composition as a function of human health and disease states have sparked remarkable interest in the human gut microbiome. However, establishing reproducible insights into the determinants of microbial succession in disease has been a formidable challenge. Results Here we use fecal microbiota transplantation (FMT) as an in natura experimental model to investigate the association between metabolic independence and resilience in stressed gut environments. Our genome-resolved metagenomics survey suggests that FMT serves as an environmental filter that favors populations with higher metabolic independence, the genomes of which encode complete metabolic modules to synthesize critical metabolites, including amino acids, nucleotides, and vitamins. Interestingly, we observe higher completion of the same biosynthetic pathways in microbes enriched in IBD patients. Conclusions These observations suggest a general mechanism that underlies changes in diversity in perturbed gut environments and reveal taxon-independent markers of “dysbiosis” that may explain why widespread yet typically low-abundance members of healthy gut microbiomes can dominate under inflammatory conditions without any causal association with disease.

Background: Patients with primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) have an increased risk of developing colorectal neoplasia (CRN) in the proximal colon. Objectives: To evaluate whether duration and severity of inflammation are linked to the development of CRN in this population. Design: Retrospective, case–control chart review of patients with PSC and IBD at a tertiary care center. Methods: Disease activity was scored per colonic segment at each colonoscopy prior to the first instance of observed CRN using a modified Mayo endoscopic sub-score and histologic assessment. Patients in the CRN-positive group were compared to controls that did not. Results: In all, 72 PSC-IBD patients with no history of CRN were identified, 13 of whom developed CRN after at least one colonoscopy at our institution. Patients in the CRN-positive group had significantly more endoscopic ( p

Background and Aims: Endoscopic assessment is a co-primary end point in inflammatory bowel disease registration trials, yet it is subject to inter- and intraobserver variability. We present an original machine learning approach to Endoscopic Mayo Score (eMS) prediction in ulcerative colitis and report the model’s performance in differentiating key levels of endoscopic disease activity on full-length procedure videos. Methods: Seven hundred ninety-three full-length videos with centrally-read eMS were obtained from 249 patients with ulcerative colitis, who participated in a phase II trial evaluating mirikizumab (NCT02589665). A video annotation approach was established to extract mucosal features and associated eMS classification labels from each video to be used as inputs for model training. The primary objective of the model was a categorical prediction of inactive vs active endoscopic disease evaluated against 2 independent test sets: a full set with a baseline single human expert read and a consensus subset in which 2 human reads agreed. Results: On the full test set of 147 videos, the model predicted inactive vs active endoscopic disease via the eMS with an area under the curve of 89%, accuracy of 84%, positive predictive value of 80%, and negative predictive value of 85%. In the consensus test set of 94 videos, the model predicted inactive vs active endoscopic disease with an area under the curve of 92%, accuracy of 89%, positive predictive value of 87%, and negative predictive value of 90%. Conclusion: We have demonstrated that this machine learning model supervised by mucosal features and eMS video annotations accurately differentiates key levels of endoscopic disease activity.

Background: Tofacitinib is an oral small molecule Janus kinase inhibitor for the treatment of ulcerative colitis (UC). Objective: To assess colectomy incidence rates (IRs) and baseline characteristics for the presence of identified colectomy risk factors among patients in the tofacitinib OCTAVE UC clinical program. Design: This post hoc analysis evaluated patients in the 8-week OCTAVE Induction 1 and 2, 52-week OCTAVE Sustain, and OCTAVE Open (open-label, long-term extension) studies. Methods: IRs [95% confidence interval (CI)] for colectomy were analyzed. Baseline risk factors based on clinical guidelines: aged 3 mg/L, and serum albumin 3 mg/L ( n = 11), and aged

Background/Aims We assessed the effectiveness of anti-TNF agents and its associated factors to prevent endoscopic and clinical postoperative recurrence (POR) in Crohn’s disease (CD). Methods From a prospectively-maintained database, we retrieved 316 CD patients who underwent intestinal resection (2011–2017). Endoscopic (Rutgeerts index ≥ i2 at 6 months) and clinical (recurrence of symptoms leading to hospitalization or therapeutic escalation) POR were assessed. Results In 117 anti-TNF-naïve patients, anti-TNF therapy was more effective than immunosuppressive agents (odds ratio [OR], 8.8; 95% confidence interval [CI], 1.8–43.9; P=0.008) and no medication/5-aminosalicylates (OR, 5.2; 95% CI, 1.0–27.9; P=0.05) to prevent endoscopic POR. In 199 patients exposed to anti-TNF prior to the surgery, combination with anti-TNF and immunosuppressive agents was more effective than anti-TNF monotherapy (OR, 2.32; 95% CI, 1.02–5.31; P=0.046) to prevent endoscopic POR. Primary failure to anti-TNF agent prior to surgery was predictive of anti-TNF failure to prevent endoscopic POR (OR, 2.41; 95% CI, 1.10–5.32; P=0.03). When endoscopic POR despite anti-TNF prophylactic medication (n=55), optimizing anti-TNF and adding an immunosuppressive drug was the most effective option to prevent clinical POR (hazard ratio, 7.38; 95% CI, 1.54–35.30; P=0.012). Anti-TNF therapy was the best option to prevent clinical POR (hazard ratio, 3.10; 95% CI, 1.09–8.83; P=0.034) in patients with endoscopic POR who did not receive any biologic to prevent endoscopic POR (n=55). Conclusions Anti-TNF was the most effective medication to prevent endoscopic and clinical POR. Combination with anti-TNF and immunosuppressive agents should be considered in patients previously exposed to anti-TNF.

Background/Aims Perianal fistulas are a debilitating manifestation of Crohn’s disease (CD). Despite the advent of anti-tumor necrosis factor (anti-TNF) therapy, the medical management of fistulizing CD continues to be challenged by unmet needs. We conducted a systematic review and meta-analysis of the effectiveness of vedolizumab for the management of perianal fistulizing CD. Methods A search of PubMed, EMBASE and the Cochrane Library was performed from inception to June 2020 for studies reporting rates of perianal fistula healing in CD patients treated with vedolizumab. The primary outcome of interest was complete healing of perianal fistulas and the secondary outcome was partial healing. The pooled fistula healing rates with 95% confidence intervals (CI) were calculated utilizing a random effects model. Results A total of 74 studies were initially identified, 4 of which met the inclusion criteria. A total of 198 patients with active perianal fistulas were included, 87% of whom had failed previous anti-TNF therapy. The pooled complete healing rate was 27.6% (95% CI, 18.9%–37.3%) with moderate heterogeneity (I2=49.4%) and the pooled partial healing rate was 34.9% (95% CI, 23.2%–47.7%) with high heterogeneity (I2=67.1%). Conclusions In a meta-analysis of 4 studies that included 198 patients with perianal fistulizing CD, the majority of whom had failed previous anti-TNF therapy, vedolizumab treatment led to healing of perianal fistulas in nearly one-third of the patients. The lack of high-quality data and significant study heterogeneity underscores the need for future prospective studies of fistula healing in patients receiving anti-integrin therapy.

Abstract Background Inflammatory bowel disease (IBD) treatment paradigms recommend objective disease activity assessment and reactive therapeutic drug monitoring (TDM) prior to changes in biologic therapy. We aimed to describe objective marker and TDM assessment in routine clinical practice prior to biologic therapeutic changes in adult IBD patients. Methods TARGET-IBD is a prospective longitudinal cohort of over 2100 IBD patients receiving usual care at 34 US academic or community centers enrolled between June 2017 and October 2019 who received biologic therapy and had a dose change or biologic discontinuation for lack of efficacy. Objective markers of disease activity within 12 weeks prior included fecal calprotectin, C-reactive protein (CRP), endoscopy, computed tomography (CT) and magnetic resonance imaging (MRI). TDM data for infliximab or adalimumab was obtained. Results 525 patients (71.4% Crohn’s disease [CD], 28.6% ulcerative colitis [UC]) receiving biologic therapy underwent dose change (55.6%) or discontinuation (44.4%) for lack of efficacy. The majority were Caucasian (85.7%), 18–39 years old (52.2%), privately insured (81.5%), and at academic centers (73.7%). For dose changes, 67.5% had at least one objective disease activity assessment or TDM in the 12 weeks prior (CD 67.9%, UC 66.2%; P = 0.79). The most common objective marker was CRP in both CD (39.1%) and UC (54.5%). CRP and calprotectin were used significantly more in UC (P = 0.02 and P = 0.03). TDM was obtained in 30.7% (28.8% UC, 31.4% CD; P = 0.72) prior to dose change. For biologic discontinuation, 79.4% patients underwent objective assessment or TDM prior. In CD, CRP (46.3%) was most common, and CT (P = 0.03) and MRI (P

Background and Aims: As inflammatory bowel disease (IBD) becomes more prevalent, the challenges that gastroenterologists face in managing these patients evolve. We aimed to describe the most important challenges facing gastroenterologists from around the world and compare these between those working in developed and developing countries. Methods: An online questionnaire was developed, and a link distributed to gastroenterologists. Data were analyzed descriptively using Friedman and Wilcoxon matched-pair signed rank tests to compare rankings for responses. Mann-Whitney U tests were used to compare rankings between responses from gastroenterologists from developed and developing countries. Lower scores reflected greater challenges. Results: Of 872 who started, 397 gastroenterologists (45.5%) completed the survey. Respondents represented 65 countries (226 [56.9%] from developed countries). Overall, the challenge ranked most important (smallest number) was increasing IBD prevalence (13.6%). There were significant differences in mean ranking scores for many simple aspects of care for those from developing countries compared to providers from developed countries, such as access to simple IBD treatments (5.52 vs. 6.02, p = 0.01), access to anti-TNF drugs including dose escalation (3.33 vs. 3.93, p < 0.01), access to good stoma care (2.57 vs. 3.03, p < 0.001), access to therapeutic drug monitoring (1.47 vs. 1.84, p < 0.001), and access to care for people from low socioeconomic status (2.77 vs. 3.37, p < 0.001). Conclusions: Increasing IBD prevalence is seen by gastroenterologists as the greatest challenge facing them. There are significant differences between the IBD challenges facing gastroenterologists from developed and developing countries that reflect inequities in access to health care.

Patients with inflammatory bowel disease (IBD) occasionally need a restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) because of medically refractory colitis or dysplasia/cancer. However, pouchitis may develop in up to 70% of patients after this procedure and significantly impair quality of life, more so if the inflammation becomes a chronic condition. About 10% of patients with IBD who develop pouchitis require pouch excision, and several risk factors of the failure have been reported. A phenotype that has features similar to Crohn’s disease may develop in a subset of ulcerative colitis patients following proctocolectomy with IPAA and is the most frequent reason for pouch failure. In this review, we discuss the diagnosis and prognosis of pouchitis, risk factors for pouchitis development, and treatment options for pouchitis, including the newer biological agents.

Introduction: Extraintestinal manifestations (EIMs) in patients with ulcerative colitis (UC) are common. Tofacitinib is an oral, small molecule Janus kinase inhibitor for the treatment of UC. We evaluated the efficacy of tofacitinib in patients with EIMs, and the impact of tofacitinib on EIMs in patients with UC in the OCTAVE clinical program. Methods: Data from two 8-week induction studies (OCTAVE Induction 1 and 2) and a 52-week maintenance study (OCTAVE Sustain) were analyzed. The effect of tofacitinib on efficacy outcomes stratified by EIM status, proportion of predefined prior and active EIMs at baseline, and change from baseline in EIMs were determined at the end of the treatment period (weeks 8 or 52), or at early termination. Results: At baseline of OCTAVE Induction 1 and 2, and OCTAVE Sustain, 27.0% and 9.0% of patients had a history of EIMs (prior or active), respectively. Patients treated with tofacitinib 10 mg twice daily (BID) achieved remission and had endoscopic improvement in all studies, irrespective of any history of EIMs. A greater proportion of patients had active peripheral arthritis at baseline of OCTAVE Induction 1 and 2 versus OCTAVE Sustain. In OCTAVE Induction 1 and 2, similar proportions of tofacitinib and placebo-treated patients with active peripheral arthritis experienced either no change (81.3% and 85.7%, respectively) or an improvement (15.6% and 14.3%, respectively). By week 52 of OCTAVE Sustain, improvements in active peripheral arthritis were only observed in tofacitinib-treated patients (16.7% and 33.3% with tofacitinib 5 and 10 mg BID, respectively). Conclusion: Any history of EIMs did not influence the efficacy of tofacitinib 10 mg BID for induction or maintenance of UC. The most common active EIM was peripheral arthritis, for which many patients in OCTAVE Induction 1 and 2, and OCTAVE Sustain, reported improvement or no change from baseline with tofacitinib treatment. Clinicaltrials.gov:NCT01465763 ; NCT01458951; NCT01458574

Depression and anxiety are comorbidities of inflammatory bowel disease (IBD). Though previous studies have proposed a relationship between anxiety, depression, and IBD, causality and directionality are largely unknown. Current and future research in these areas is aimed at exploring the biological underpinnings of this relationship, specifically pertaining to small molecule metabolism, such as tryptophan. Tryptophan is acquired through the diet and is the precursor to several vital bioactive metabolites including the hormone melatonin, the neurotransmitter serotonin, and vitamin B3. In this review, we discuss previous findings relating mental health comorbidities with IBD and underline ongoing research of tryptophan catabolite analysis.

Enteric infections have previously been postulated to play a role in the pathogenesis of inflammatory bowel disease (IBD), however, little evidence exists in the etiologic role of specific enteric infections in the development of IBD. When encountered in the setting of IBD, enteric infections pose a clinical challenge in management given the competing treatment strategies for infectious conditions and autoimmune disorders. Here we present the case of a young male with enteric infections complicating a new diagnosis of IBD. Our patient's initial clinical presentation included diagnoses of Klebsiella oxytoca isolation and Clostridium difficile infection. Directed therapies to include withdrawal of antibiotics and fecal microbiota transplantation were performed without resolution of clinical symptoms. Given persistence of symptoms and active colitis, the patient was diagnosed with ulcerative colitis (UC), requiring treatments directed at severe UC to include cyclosporine therapy. The finding of multiple enteric infections in a newly presenting patient with IBD is an unexpected finding that has treatment implications.

Abstract Background Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection and shows promise for treating other medical conditions associated with intestinal dysbioses. However, we lack a sufficient understanding of which microbial populations successfully colonize the recipient gut, and the widely used approaches to study the microbial ecology of FMT experiments fail to provide enough resolution to identify populations that are likely responsible for FMT-derived benefits. Methods We used shotgun metagenomics together with assembly and binning strategies to reconstruct metagenome-assembled genomes (MAGs) from fecal samples of a single FMT donor. We then used metagenomic mapping to track the occurrence and distribution patterns of donor MAGs in two FMT recipients. Results Our analyses revealed that 22% of the 92 highly complete bacterial MAGs that we identified from the donor successfully colonized and remained abundant in two recipients for at least 8 weeks. Most MAGs with a high colonization rate belonged to the order Bacteroidales. The vast majority of those that lacked evidence of colonization belonged to the order Clostridiales, and colonization success was negatively correlated with the number of genes related to sporulation. Our analysis of 151 publicly available gut metagenomes showed that the donor MAGs that colonized both recipients were prevalent, and the ones that colonized neither were rare across the participants of the Human Microbiome Project. Although our dataset showed a link between taxonomy and the colonization ability of a given MAG, we also identified MAGs that belong to the same taxon with different colonization properties, highlighting the importance of an appropriate level of resolution to explore the functional basis of colonization and to identify targets for cultivation, hypothesis generation, and testing in model systems. Conclusions The analytical strategy adopted in our study can provide genomic insights into bacterial populations that may be critical to the efficacy of FMT due to their success in gut colonization and metabolic properties, and guide cultivation efforts to investigate mechanistic underpinnings of this procedure beyond associations.

Background/AimsUlcerative colitis (UC) patients are at greater risk for the development of colorectal neoplasia. Several individual studies have demonstrated associations between severity of histologic inflammation and colorectal neoplasia. However, a comprehensive systematic review has not been completed. We performed a systematic review and meta-analysis to explore the relationship between histologic inflammation and risk for neoplasia among available observational studies.MethodsThree databases (EMBASE, MEDLINE and the Cochrane Library) were systematically searched. Studies were included if they included UC patients who underwent colonoscopic assessment and when histologic inflammation and colorectal neoplasia were both reported. Colorectal neoplasia rates were compared. Quantitative meta-analysis was attempted.ResultsFour of 1,422 records found were eligible. Results from 2 case-control studies reported a 3.5-fold increased risk for colorectal neoplasia associated with a single point increase in histologic inflammation. This result was further corroborated by one cohort study that demonstrated increased hazard ratios. The second cohort study reported outcomes for patients with normal gross endoscopy, but had increased histological inflammation when neoplasia was assessed. Finally, this study reported increased risk for neoplastic progression by histological inflammation among patients who were normal by gross endoscopic evaluation. Quantitative meta-analysis was unsuccessful due to heterogeneity between study measures.ConclusionsThere is strong evidence that histologic inflammation among patients with UC increases the risk of colorectal neoplasia. The depth and nature of assessment of additional clinical variables was varied and may have resulted in greater outcome discrepancy. Additional study related to mechanisms of inflammation-related neoplasia and therapeutic modification is needed.

ABSTRACT A 2-year longitudinal microbiome study of 22 patients who underwent colectomy with an ileal pouch anal anastomosis detected significant increases in distinct populations of Bacteroides during 9 of 11 patient visits that coincided with inflammation (pouchitis). Oligotyping and metagenomic short-read annotation identified Bacteroides populations that occurred in early samples, bloomed during inflammation, and reappeared after antibiotic treatment. Targeted cultivation of Bacteroides isolates from the same individual at multiple time points and from several patients detected subtle genomic changes, including the identification of rapidly evolving genomic elements that differentiate isogenic strains of Bacteroides fragilis from the mucosa versus lumen. Each patient harbored Bacteroides spp. that are closely related to commonly occurring clinical isolates, including Bacteroides ovatus, B. thetaiotaomicron, B. vulgatus, and B. fragilis, which contained unique loci in different patients for synthesis of capsular polysaccharides. The presence of unique Bacteroides capsular polysaccharide loci within different hosts and between the lumen and mucosa may represent adaptations to stimulate, suppress, and evade host-specific immune responses at different microsites of the ileal pouch. IMPORTANCE This longitudinal study provides an opportunity to describe shifts in the microbiomes of individual patients who suffer from ulcerative colitis (UC) prior to and following inflammation. Pouchitis serves as a model for UC with a predictable incidence of disease onset and enables prospective longitudinal investigations of UC etiology prior to inflammation. Because of insufficient criteria for predicting which patients will develop UC or pouchitis, the interpretation of cross-sectional study designs suffers from lack of information about the microbiome structure and host gene expression patterns that directly correlate with the onset of disease. Our unique longitudinal study design allows each patient to serve as their own control, providing information about the state of the microbiome and host prior to and during the course of disease. Of significance to the broader community, this study identifies microbial strains that may have genetic elements that trigger the onset of disease in susceptible hosts.

As biologic-based medication options for ulcerative colitis expand, our understanding of their optimal use in clinical practice is advancing as well. The appropriate use of combination therapy with immunomodulators can reduce the immunogenicity of biologic agents and raise serum drug levels of the biologic. A treat-to-target strategy with objective assessments of disease activity clearly defines the goals of biologic drug treatment. Mucosal healing is an evolving treatment goal and is associated with long-term remission and reduced incidence of colectomy. Furthermore, regular reassessments and therapeutic drug monitoring can allow clinicians to make evidence-based changes in therapy. Biologic drug de-escalation or re-initiation are less well developed topics, but are emerging areas of study. We review the evidence underlying these advances and a modern approach to the use of biologic therapy in ulcerative colitis.

Objectives. This open-label trial assessed the efficacy and safety of rifaximin as first-line therapy in hospitalized patients with Clostridium difficile-associated diarrhea (CDAD). Methods. We enrolled thirteen patients who had a confirmed diagnosis of CDAD characterized by ≥3 unformed stools/day and positive C. difficile toxin assay. Those patients received rifaximin 400 mg three times daily for 10 days. Resolution of symptoms, repeat assay 10 days after treatment, and followup for recurrence were assessed. Results. Eight patients completed the study, and all reported symptom resolution during treatment. Mean time to last unformed stool was 132 h ± 42.5 h. Seven patients had no relapse by week 2 and in longer followup (median 162 days). One patient had recurrent CDAD during a repeat hospitalization. Conclusions. Rifaximin was effective and safe as first-line treatment for CDAD and did not result in recurrence in most patients.