The Odoribacter splanchnicus strain of human donor-derived bacteria correlated with clinical response to ulcerative colitis in study in which mouse models were colonized with patient-derived strains.
Although some recent trials have shown the effectiveness of fecal microbiota transplantation (FMT) for patients with ulcerative colitis (UC), the current process is limited by the used of crude donor fecal material, which increases the risk of infection and decreases potential effectiveness, Svetlana Lima, MD, of Weill Cornell Medicine, New York, and colleagues wrote.
“Rational selection and production of specific microbial strains or communities could improve efficacy, minimize the risk of adverse reactions as well as increase the acceptance of microbiome-based therapies,” the researchers wrote.
In a study published in Gastroenterology, the researchers used metagenomic analysis and IgA sequencing (for sorting and sequencing IgA-coated microbiota) to identify a core of transferable and IgA-coated microbiota. They conducted metagenomic sequencing on 60 stool samples, including 20 recipient-participants with active UC who were treated with FMT, and another 20 FMT recipients with data from 4 weeks after FMT from a previously reported trial.
The core transferable microbiota (CTM) included 22 species of bacteria at 4 weeks after FMT. To determine a relationship between CTM and clinical response to FMT, the researchers defined clinical response as a decrease in Mayo score of 3 or greater with a rectal bleeding score of 1 or less by 4 weeks after FMT; 35% of study participants met this endpoint.* A total of 20 species were unique to the responders. “Of the donor-derived genera, only the relative abundance of Odoribacter at [week 4] post FMT and its increase post FMT was found to significantly correlate with decrease in Mayo score,” the researchers noted.
The researchers then colonized germ-free or genetically engineered mice with patient-derived bacterial strains.
O. splanchnicus also increased induction of interleukin-10, and increased the production of short-chain fatty acids. Taken together, these factors allowed for O. splanchnicus to limit colitis in the mice.
The study findings represent the first strain-level analysis of FMT in UC participants, and define a transferable microbiota associated with clinical response that could serve as a prognostic biomarker, the researchers noted in their discussion section. Although analysis revealed 12 donor-derived bacterial species that predicted clinical response, further IgA analysis identified O. splanchnicus as “the only microbe within the responders core that correlates with clinical response and highlights the potential impact of this taxa seen in independent cohorts, as well as mouse models of colitis and colorectal cancer,” the researchers emphasized.
The study findings were limited by the small sample size and the lack of prospective data. However, “collectively, this work provides the first evidence of transferable, donor-derived strains that correlate with clinical response to FMT in UC and reveals O. splanchnicus as a key component, which mechanistically promotes protection through both cellular and metabolic function,” the researchers said. “These mechanistic features will help enable desperately needed strategies to enhance therapeutic efficacy of microbial therapy for UC.”
Study strains improve effectiveness
Dr. Jeffrey Berinstein
“There is an accumulating body of evidence that suggests that gut dysbiosis, or the imbalance between good and bad microbes, plays an important role in the pathogenesis and progression of ulcerative colitis,” Jeffrey Berinstein, MD, of the University of Michigan, Ann Arbor, said in an interview. “It is for this reason that therapeutic manipulation of gut microbiota with fecal microbiota transplant is being explored as a potential treatment option for UC. FMT has demonstrated promise for ulcerative colitis, however little is known about the specific microbiota strains contributing to this observed improvement. In this study, the authors aimed to better understand the mechanisms and the specific strains in FMT contributing to this observed improvement, which is an important step toward improving efficacy and minimizing the risk of adverse events related to FMT in the future.”
Dr. Berinstein was surprised that O. splanchnicus was the only microbe identified that correlated with clinical response. “Previous studies have suggested that microbial diversity is a key factor in successful response to FMT,” he noted. “FMT remains an important potential nonpharmacologic treatment strategy for ulcerative colitis, however more research is needed to understand the mechanism and to develop safer and more efficacious methods for delivering FMT.” Specifically, prospective studies are needed to explore the efficacy and safety of FMT enriched in strains of O. splanchnicus to confirm the current study findings.
Dr. Atsushi Sakuraba
The current study is important at this time because, although microbial transferability has emerged as a potential to treat IBD, “the mechanistic understanding of microbial transferability and engraftment has been lacking,” Atsushi Sakuraba, MD, PhD of the University of Chicago, said in an interview. “I was surprised that the effectiveness of FMT in UC could be narrowed down to O. splanchnicus.” The current take-home message for clinicians is that, although FMT currently uses crude donor fecal material, it may soon use more selected microbial strains. However, “whether transfer of O. splanchnicus alone or enriched fecal material provide improved efficacy and safety need to be analyzed,” he added.
The study was supported by Boehringer Ingelheim, the National Institutes of Health, the Kenneth Rainin Foundation, and the Charina Foundation. One coauthor disclosed grant support from Boehringer Ingelheim for this study, and several coauthors are employees of Boehringer Ingelheim. Neither Dr. Berinstein nor Dr. Sakuraba had no financial conflicts to disclose.
This article was updated Dec. 1, 2021.
*Correction, 4/11/22: An earlier version of this article misstated the definition of clinical response.