Staphylococcus aureus is a common bacteria species in humans, but it can turn nasty if it gets into the wrong part of the body. A new clinical trial has shown that a probiotic can be used to selectively cut populations of the bug in humans, reducing the risk of infection without the hazards of antibiotics.
S. aureus can be found in the nose, gut and on the skin of many people, and for the most part it’s harmless there. But if it gets into a wound, the bloodstream, the lungs or anywhere else it isn’t meant to be, it can cause serious infections. Worse still, it’s increasingly resistant to antibiotics, with a particularly dangerous form called Methicillin-resistant S. aureus (MRSA) or “golden staph” becoming a common hospital-acquired infection.
Reducing the harmless populations in the body has been suggested as a way to reduce the risk of serious infections, but doing so using antibiotics isn’t ideal since it can fuel further drug resistance and also wipes out good bacteria in the gut.
For the new study, researchers at the National Institute of Allergy and Infectious Diseases (NIAID) investigated using probiotics instead. In previous studies, the team had found that certain molecules produced by another bacteria called Bacillus subtilis interfered with the sensing system of S. aureus, which stops the latter from growing. B. subtilis is already in use as a human probiotic.
In the new clinical trial, 115 participants that naturally hosted colonies of S. aureus were given either B. subtilis or a placebo every day for 30 days. After that, the researchers evaluated the levels of the bacteria in their noses and gut, and compared it to levels from the beginning of the trial. And sure enough, those receiving the probiotic saw a 96.8% reduction of S. aureus populations in their gut, and a 65.4% reduction in the nose. Meanwhile, no changes were detected in the control group.
“The probiotic we use does not ‘kill’ S. aureus, but it specifically and strongly diminishes its capacity to colonize,” said Dr. Michael Otto, lead researcher on the trial. “We think we can target the ‘bad’ S. aureus while leaving the composition of the microbiota intact.”
The team says that the technique could be an effective preventative treatment for people at a higher risk of infection by S. aureus. Since B. subtilis is already widely used as a probiotic, it’s much safer than antibiotics for long-term use.
The researchers are planning to follow it up with another trial that tests more people over a longer period of time.
The study was published in the journal The Lancet Microbe.