Immune checkpoint inhibitor-mediated colitis is associated with cancer overall survival.

BACKGROUND: Immune checkpoint inhibitor-mediated colitis (IMC) is a common adverse event following immune checkpoint inhibitor (ICI) therapy for cancer. IMC has been associated with improved overall survival (OS) and progression-free survival (PFS), but data are limited to a single site and predominantly for melanoma patients. AIM: To determine the association of IMC with OS and PFS and identify clinical predictors of IMC. METHODS: We performed a retrospective case-control study including 64 ICI users who developed IMC matched according to age, sex, ICI class, and malignancy to a cohort of ICI users without IMC, from May 2011 to May 2020. Using univariate and multivariate logistic regression, we determined association of presence of IMC on OS, PFS, and clinical predictors of IMC. Kaplan-Meier curves were generated to compare OS and PFS between ICI users with and without IMC. RESULTS: IMC was significantly associated with a higher OS (mean 24.3 mo vs 17.7 mo, P = 0.05) but not PFS (mean 13.7 mo vs 11.9 mo, P = 0.524). IMC was significantly associated with OS greater than 12 mo [Odds ratio (OR) 2.81, 95% confidence interval (CI) 1.17-6.77]. Vitamin D supplementation was significantly associated with increased risk of IMC (OR 2.48, 95%CI 1.01-6.07). CONCLUSION: IMC was significantly associated with OS greater than 12 mo. In contrast to prior work, we found that vitamin D use may be a risk factor for IMC.

Changes in Colonic Bile Acid Composition following Fecal Microbiota Transplantation Are Sufficient to Control Clostridium difficile Germination and Growth.

Fecal microbiota transplantation (FMT) is a highly effective therapy for recurrent Clostridium difficile infection (R-CDI), but its mechanisms remain poorly understood. Emerging evidence suggests that gut bile acids have significant influence on the physiology of C. difficile, and therefore on patient susceptibility to recurrent infection. We analyzed spore germination of 10 clinical C. difficile isolates exposed to combinations of bile acids present in patient feces before and after FMT. Bile acids at concentrations found in patients' feces prior to FMT induced germination of C. difficile, although with variable potency across different strains. However, bile acids at concentrations found in patients after FMT did not induce germination and inhibited vegetative growth of all C. difficile strains. Sequencing of the newly identified germinant receptor in C. difficile, CspC, revealed a possible correspondence of variation in germination responses across isolates with mutations in this receptor. This may be related to interstrain variability in spore germination and vegetative growth in response to bile acids seen in this and other studies. These results support the idea that intra-colonic bile acids play a key mechanistic role in the success of FMT, and suggests that novel therapeutic alternatives for treatment of R-CDI may be developed by targeted manipulation of bile acid composition in the colon.

Microbiota transplantation restores normal fecal bile acid composition in recurrent Clostridium difficile infection.

Fecal microbiota transplantation (FMT) has emerged as a highly effective therapy for refractory, recurrent Clostridium difficile infection (CDI), which develops following antibiotic treatments. Intestinal microbiota play a critical role in the metabolism of bile acids in the colon, which in turn have major effects on the lifecycle of C. difficile bacteria. We hypothesized that fecal bile acid composition is altered in patients with recurrent CDI and that FMT results in its normalization. General metabolomics and targeted bile acid analyses were performed on fecal extracts from patients with recurrent CDI treated with FMT and their donors. In addition, 16S rRNA gene sequencing was used to determine the bacterial composition of pre- and post-FMT fecal samples. Taxonomic bacterial composition of fecal samples from FMT recipients showed rapid change and became similar to the donor after the procedure. Pre-FMT fecal samples contained high concentrations of primary bile acids and bile salts, while secondary bile acids were nearly undetectable. In contrast, post-FMT fecal samples contained mostly secondary bile acids, as did non-CDI donor samples. Therefore, our analysis showed that FMT resulted in normalization of fecal bacterial community structure and metabolic composition. Importantly, metabolism of bile salts and primary bile acids to secondary bile acids is disrupted in patients with recurrent CDI, and FMT corrects this abnormality. Since individual bile salts and bile acids have pro-germinant and inhibitory activities, the changes suggest that correction of bile acid metabolism is likely a major mechanism by which FMT results in a cure and prevents recurrence of CDI.

High-throughput DNA sequence analysis reveals stable engraftment of gut microbiota following transplantation of previously frozen fecal bacteria.

Fecal microbiota transplantation (FMT) is becoming a more widely used technology for treatment of recurrent Clostridum difficile infection (CDI). While previous treatments used fresh fecal slurries as a source of microbiota for FMT, we recently reported the successful use of standardized, partially purified and frozen fecal microbiota to treat CDI. Here we report that high-throughput 16S rRNA gene sequencing showed stable engraftment of gut microbiota following FMT using frozen fecal bacteria from a healthy donor. Similar bacterial taxa were found in post-transplantation samples obtained from the recipients and donor samples, but the relative abundance varied considerably between patients and time points. Post FMT samples from patients showed an increase in the abundance of Firmicutes and Bacteroidetes, representing 75-80% of the total sequence reads. Proteobacteria and Actinobacteria were less abundant (< 5%) than that found in patients prior to FMT. Post FMT samples from two patients were very similar to donor samples, with the Bacteroidetes phylum represented by a great abundance of members of the families Bacteroidaceae, Rikenellaceae and Porphyromonadaceae, and were largely comprised of Bacteroides, Alistipes and Parabacteroides genera. Members of the phylum Firmicutes were represented by Ruminococcaceae, Lachnospiraceae, Verrucomicrobiaceae and unclassified Clostridiales and members of the Firmicutes. One patient subsequently received antibiotics for an unrelated infection, resulting in an increase in the number of intestinal Proteobacteria, primarily Enterobacteriaceae. Our results demonstrate that frozen fecal microbiota from a healthy donor can be used to effectively treat recurrent CDI resulting in restoration of the structure of gut microbiota and clearing of Clostridum difficile.