A probiotic supplement appears to clear the body of a type of bacteria that can cause serious antibiotic-resistant infections, a new study finds.
More research is needed, but experts said the work could lead to a way to prevent infections with the bacteria, called Staphylococcus aureus.
S. aureus most commonly causes skin infections, but can also lead to serious, potentially fatal disease if it enters the bloodstream. Of particular concern are methicillin-resistant S. aureus (MRSA) strains — so-called “superbugs” that are resistant to many of the antibiotics used to treat staph infections.
That’s why researchers have looked for ways to prevent staph infections in the first place.
The human body naturally harbors S. aureus, with the nose and skin being two hot spots. So researchers have tried using topical antibiotics or antiseptics to eradicate staphylococci in those body parts, in certain higher-risk situations, such as when people are hospitalized or on kidney dialysis.
But success has been limited, says Michael Otto, a senior research scientist at the U.S. National Institute of Allergy and Infectious Diseases.
He pointed to what is considered a major obstacle: the gut is an even larger “reservoir” for S. aureus, quickly replenishing supplies depleted in the nose or skin.
That’s a formidable problem, because there hasn’t been a safe way to target S. aureus specifically in the gut.
“It’s just not possible to use oral antibiotics,” Otto said. That, he explained, would indiscriminately knock out the “good” bacteria that normally live in the gut and support vital bodily functions.
For the new study, Otto and his colleagues tried a different tactic: a probiotic called Bacillus subtilis. They chose that bacteria in part based on a curious finding from a 2018 study: People who had Bacillus in their stools never had S. aureus in their bodies.
Not everyone carries a permanent “colony” of S. aureus, Otto explained. Research shows that about a third of the population does this, for unclear reasons.
But carrying Bacillus can be a protective factor. In their previous work, Otto’s team also found that most species of Bacillus, including most B. subtilis strains, secrete substances that specifically inhibit S. aureus from gaining a foothold in the body.
All this raised the possibility that Bacillus could be used to selectively deplete S. aureus while leaving other gut bacteria alone.
The current study involved 115 healthy adults from Thailand whose nasal and stool samples indicated they were permanent carriers of S. aureus. They were randomly assigned to take the B. subtilis supplement or placebo capsules every day for 30 days.
Ultimately, the study found that the probiotic nearly wiped out S. aureus in the gut, reducing the amount of stool samples from the participants by an average of 97%. It also reduced levels of the bacteria in nasal samples by two-thirds.
Just as importantly, Otto’s team found that there were no signs that the probiotic had harmful effects on the normal bacterial composition of the gut.
The findings were recently published in the journal Lancet Microbe.
An infectious disease specialist not involved in the trial called the findings “very interesting.”
However, more research is needed to see if the probiotic is safe and effective for long-term use — and if it actually prevents staph infections, said Dr. Aaron Glatt, a spokesperson for the Infectious Diseases Society of America.
At this point, he said, no one should be running to the health food store to stock up on Bacillus. First, supplements aren’t regulated like drugs, and there’s no guarantee of what you buy, said Glatt, who is also chief of infectious diseases at Mount Sinai South Nassau in Oceanside, NY.
Aside from that, most people would have little need for a probiotic to clear out S. aureus roaming the body.
Otto said the potential application would be in preventing S. aureus infections in certain people at higher risk, such as those who have a history of recurrent infections or patients on kidney dialysis.
The probiotic doesn’t actually “kill” S. aureus, Otto noted, but instead inhibits its ability to establish a colony. So it wouldn’t treat an established staph infection.
Why do some people carry a healthy supply of Bacillus? It’s not entirely clear, but Otto noted that the 2018 study was also conducted in rural Thailand, where many people may have ingested the bacteria from plant foods that had not been washed. (Bacillus is abundant in the soil.)
But Otto said he wouldn’t advocate eating unwashed fruits and vegetables in hopes of ingesting Bacillus.