Inactivated probiotic shows benefit in IBS symptoms

An oral preparation containing heat-inactivated Bifidobacterium bifidum provides a modest improvement in symptoms for adults with IBS, according to a RCT.

And such a preparation might offer advantages over living probiotics such as better standardisation, greater stability and improved safety, the researchers said.

The German study randomised 443 patients from 20 sites to either the morphologically intact but non-viable B. bifidum MIMBb75 or placebo capsules twice daily for eight weeks.

Participants met all ROME lll criteria for IBS. They included constipation predominant IBS (24%), diarrhoea predominant IBS (43%), mixed IBS (6%) and unknown subtype IBS (26%).

The primary endpoint, a composite of pain response and global relief response, was achieved by 34% of the treated group compared to 19% of the control group (p=0.0007).

The study, published in The Lancet Gastroenterology & Hepatology, said the number needed to treat for benefit was 7.1.

Secondary endpoints, such as the IBS Severity Scoring System (IBS-SSS), the subject’s global assessment of IBS symptoms, and a health-related quality of life score (SF-12), also consistently indicated a statistically significant benefit from the B. bifidum preparation.

“Compared with placebo, B bifidum HI-MIMBb75 was associated with 1·7 times greater response rate for the composite primary endpoint, defined as a combination of at least a 30% improvement of abdominal pain together with significant adequate relief of global IBS symptoms in at least 50% of the treatment period,” the study authors said.

“Additionally, patients receiving B bifidum HI-MIMBb75 had greater relief of individual IBS symptoms, including abdominal pain, distension and bloating, discomfort, pain associated with bowel movement, and frequency of bowel movement.”

Medications taken for IBS symptoms were similar in both groups and the tolerability of the intervention was typically reported as good or very good in both groups.

However an accompanying editorial by researchers from the Hunter Medical Research Institute said while the concept that non-viable organisms might be efficacious in IBS was important, there was still much more to learn.

“A strength of the study was that all IBS subtypes were included in the analysis, and the inactivated bacterial therapy appeared to benefit the different subgroups,” they said.

“However, the mechanism of action of B. bifidum in IBS is unknown.”

The team, including Professor Nick Talley and Professor Simon Keely, said the suggestion that non-viable B. bifidum could improve intestinal barrier function required more evidence.

“Alternatively, heat inactivating the organisms might release anti-bacterial molecules that impinge on other key bacteria that are important in the pathogenesis of IBS, but this hypothesis is speculative.”

“Furthermore, the patient’s microbiome does not appear to permanently change, and the benefits of probiotic therapy therefore appear to rely on repeat administration, because stopping therapy results in any relief quickly resolving.”

“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.

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