Oral Probiotic Bacillus Prevents Enterococcal Sepsis in Mouse Study

Oral Probiotic Bacillus Prevents Enterococcal Sepsis in Mouse Study

NIAID intramural scientists have shared an unexpected finding in their continuing study of a common probiotic digestive supplement, Bacillus bacteria, as a treatment for bacterial gut infections. Bacillus given orally stopped colonizing pathogenic Enterococcus faecalis from spreading into the bloodstream and causing a system-wide infection known as sepsis.

Enterococcal bacteria, like Staphylococcal bacteria, are of great research interest to scientists because they easily colonize in people, are resistant to most antibiotics, and can lead to severe disease and death. For example, in 2017 the CDC estimated there were more than 5,000 deaths and 50,000 cases of Enterococcal disease stemming from cases resistant to the antibiotic vancomycin.

People at highest risk of severe disease from Enterococcal infection include those who have undergone lengthy antibiotic treatment; those who are in the hospital, have recently had surgery or who have an invasive medical devise such as a catheter; and those with weakened immune systems, such as ICU, cancer, and transplant patients.

In 2018 the same NIAID researchers, led by Michael Otto, Ph.D., published findings showing that people who had Bacillus in their gut never were colonized with S. aureus in their gut or nose. Then, using a mouse study model, they identified exactly how that happens: Bacillus produces substances that shut down a key bacterial sensing mechanism in S. aureus.

Because S. aureus and E. faecalis have similar sensing mechanisms, the scientists decided to examine in mice whether Bacillus also would prevent gut colonization of E. faecalis. It did not, as shown in their latest study, published in Science Translational Medicine. But Bacillus did surprisingly prevent E. faecalis from becoming septic, a significant finding for human health. Like in the 2018 study of S. aureus, the scientists subsequently learned precisely how E. faecalis moves from the gut to the bloodstream and how Bacillus potentially could prevent that movement.

Compared to traditional drug treatment, “… the probiotic approach proposed in this study, which uses orally administered B. subtilis spores that germinate in the intestine, has the advantage that the inhibiting molecules are constantly being produced by an administered probiotic live organism,” the study states. Also, probiotics are generally healthy and do not cause the disadvantages of antibiotic therapy, such as  indiscriminately destroying all bacteria, which can lead to the overgrowth of E. faecalis and other pathogenic bacteria.

The scientists are continuing their research by trying to determine how E. faecalis spreads elsewhere in the body, such as to different organs, and whether that spread can be prevented.

Reference: P Piewngam, et al. Enterococcal bacteremia in mice is prevented by oral administration of probiotic Bacillus spores. Science Translational Medicine DOI: 10.1126/scitranslmed.abf4692 (2021).