pointing the way to a therapeutic path that could avoid some risks of live probiotic use.
Of 443 patients taking part in a randomized, double-blind, placebo-controlled trial of a heat-inactivated nonviable Bifidobacterium probiotic, 221 received the probiotic while 222 received placebo capsules. The study’s primary endpoint was a composite of at least 30% improvement in abdominal pain and “adequate relief” of overall irritable bowel syndrome (IBS) symptoms in at least 4 of the 8 weeks of the study.
Within the B. bifidum group, 74 patients (34%) reached this endpoint, compared with 43 (19%) of those in the placebo group, for a risk ratio of 1.7 (P = .0007). Patients had no serious adverse events from the oral therapy, which they took in the form of two capsules daily for 8 weeks, and participants found both the inactivated Bifidobacterium treatment and placebo tolerable overall.
Bowel movements became more frequent in those who received B. bifidum capsules who had constipation-predominant IBS and less frequent in those with diarrhea-predominant IBS; the changes were statistically significant in both subgroups.
“Some probiotic strains can adhere well to epithelial cells and strengthen intestinal barrier function, providing an explanation for the efficacy of at least some probiotics in the treatment of IBS,” wrote Viola Andresen, MD, MSc, the study‘s lead author.
“Accordingly, enhancing the gut barrier is a useful treatment approach for patients with IBS,” added Dr. Andresen, of the department of internal medicine at the University of Hamburg (Germany) Teaching Hospital, and collaborators. The adherent properties of some strains of Bifidobacteria are mainly dependent on properties of the cell surface that are not changed by heat inactivation, which makes the bacteria nonviable – and removes the risk of infection.
Additional benefits of using nonviable bacteria for IBS therapy might include more stability and enhanced standardization, although previous studies have shown a reduction in efficacy when bacteria are made nonviable. Inactivated B. bifidum MIMBb75 was used in this study because it had previously been shown effective against IBS symptoms, noted Dr. Andresen and coauthors.
Adult patients were included if they met criteria for IBS according to Rome III and had abdominal pain rated at least 4 on an 11-point scale for at least 2 days of a 2-week run-in phase. Among the many criteria for exclusion from the study were history of inflammatory gastrointestinal disease, cancer, other serious stomach diseases, diabetes, many abdominal surgeries, and recent antipsychotic or steroid use.
During the study, participants recorded their abdominal pain over the last 24 hours daily; weekly averages were tallied for each patient. Patients were also asked to rate their relief of IBS symptoms, including abdominal pain, bowel habits, and other symptoms over the past week at weekly time points on a 7-point Likert scale, where scores of 3 or less indicated some measure of relief; IBS symptoms were considered to be adequately relieved with a score of 3 or less.
Secondary outcome measures for the study included changes in the Subjects’ Global Assessment of symptoms, and changes in individual symptoms. Number of bowel movements, stool form, sensation of incomplete evacuation, and medication use were also recorded daily.
Participants were aged a mean of 41 years, and about 70% were female. The mean body mass index was just under 25 kg/m2. About half of each study arm had diarrhea-predominant IBS. About a quarter had constipation-predominant IBS, and most of the rest were not subtyped.
Looking at the primary endpoint, the number needed to treat for benefit was 7.1 in favor of the inactivated bacterium, using an intention-to-treat analysis. Results were similar when a per-protocol analysis was applied. The investigators saw response to treatment climb through the duration of the study for both the probiotic and the placebo arms, with the gap in improvement between the groups widening over the 8-week study period.
“It might be assumed that the use of nonviable bacteria for the treatment of IBS could be a safe alternative, even in patients who are potentially susceptible to infection,” concluded Dr. Andresen and colleagues. A further advantage, noted the researchers, is greater product stability in fluctuating temperatures compared with viable bacteria, ensuring better standardization even in regions with warm or changing climates.
Perspective was offered in an accompanying commentary whose lead author was, a gastroenterologist, adjunct professor, and pro vice-chancellor for global research at the University of Newcastle (Australia).
“By heat inactivating the bacteria the researchers did not administer a probiotic but a bacterial therapy,” wrote Dr. Talley and coauthors. In any event, they added, the exact mechanism by which probiotics benefit individuals with IBS is unknown.
“The concept that a probiotic might be efficacious in IBS even if nonviable organisms are administered is an important observation,” they wrote. Fewer benefits have been seen with oral probiotic therapy than with fecal microbial transfer, and oral therapy does not produce durable results unless administered on a chronic basis, Dr. Talley and coauthors added.
“The absence of fundamental knowledge in terms of how bacterial therapy alters mechanisms in IBS continues to hamper improvements in treatment, limiting any success to short-term symptom control rather than the true goal, reversal of disease,” they concluded.
The study was funded by Synformulas. Dr. Andresen reported financial relationships with several pharmaceutical companies. Dr. Talley reported financial relationships with several pharmaceutical and nutritional companies.
SOURCE: Andresen V et al. Lancet Gastroenterol Hepatol. 2020 Apr 8.