A new study finds that a probiotic supplement appears to cleanse the body of a type of bacteria that can cause serious infections that are resistant to antibiotics.
More research is needed, but experts said the work could lead to a way to prevent infection with the bacteria, called Staphylococcus aureus.
Staphylococcus aureus usually causes skin infections, but it can also lead to serious illness and even death if it gets into the bloodstream. Of particular concern are strains of methicillin-resistant Staphylococcus aureus (MRSA) – so-called “superbugs” that are resistant to many of the antibiotics used to treat staph infections.
Given this, researchers sought ways to prevent staph infections in the first place.
The human body naturally contains S. aureus bacteria, with the nose and skin being hot spots. So researchers have tried using topical antibiotics or antiseptics to kill staph in those areas of the body, in some of the more serious situations — like people being hospitalized or undergoing dialysis.
Success has been limited, said Michael Otto, a senior investigator at the US National Institute of Allergy and Infectious Diseases.
He pointed to what he thinks is a major snag: The gut is a larger “reservoir” for S. aureus, and it rapidly replenishes a supply that is depleted in the nose or skin.
This is an enormous problem, because there is no safe way to specifically target S. aureus bacteria in the gut.
“It’s simply not possible to use oral antibiotics,” Otto said. This, he explained, would indiscriminately kill the “good” bacteria that normally live in the gut and support vital body functions.
For the new study, Otto and his colleagues tried a different tactic: a probiotic called Bacillus subtilis. They chose the bacterium based in part on an intriguing finding from a 2018 study: People who became infected with Bacillus in their feces never harbored S. aureus in their bodies.
Otto explained that not everyone carries a permanent “colony” of S. aureus. Research indicates that about a third of the population does so for reasons that are not clear.
However, carrying Bacillus may be a protective factor. In their previous work, Otto’s team also found that most species of bacillus, including most strains of Bacillus subtilis, secrete substances that specifically prevent S. aureus from gaining a foothold in the body.
All of which raised the possibility of using Bacillus to selectively deplete S. aureus while leaving other gut bacteria alone.
The current study included 115 healthy adults from Thailand whose nasal and fecal samples indicated that they were frequent carriers of S. aureus. They were randomly assigned to take B. subtilis supplements or placebo capsules every day for 30 days.
In the end, the study found that the probiotics nearly eliminated S. aureus bacteria in the gut, reducing the amount of participants’ stool samples by an average of 97%. It also reduced levels of bacteria in nasal samples by two-thirds.
Equally important, Otto’s team found that there were no signs that probiotics had harmful effects on the normal bacterial composition of the gut.
The results were recently published in The Lancet Microbe.
An infectious disease specialist who was not involved in the trial called the results “very interesting”.
However, more research is needed to see if probiotics are safe and effective for long-term use — and whether they actually prevent 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 bacilli. For example, dietary supplements aren’t regulated like drugs, and there’s no guarantee what you’re buying, said Glatt, who is also chief of infectious diseases at Mount Sinai South Nassau in Oceanside, New York.
Furthermore, most people will not need to take a probiotic just to clear out any S. aureus circulating in the body.
A potential application, Otto said, would be in preventing S. aureus infections in certain people who are at higher risk — such as those who have had frequent infections in the past, or patients on dialysis.
Otto noted that probiotics don’t actually “kill” S. aureus, but rather hinder its ability to establish a colony. So it will not treat proven staph infections.
Why do some people carry a healthy supply of bacilli? It’s not entirely clear, but Otto notes that the 2018 study was also conducted in rural Thailand, where many people may have ingested bacteria from plant foods that have not been washed. (Bacilli are abundant in the soil).
But Otto said he wouldn’t advocate eating unwashed fruits and vegetables in the hope that they’d load up on bacilli.