An unexpected finding in a study by National Institute of Health (NIH) researchers suggests that a “good” bacterium commonly found in probiotic digestive supplements works against Staphylococcus aureus (S aureus) .
The researchers recruited 200 volunteers in Thailand for the study. They speculated that Thais would not be as affected by food sterilization or antibiotics as people in highly developed urban areas. The researchers analyzed fecal samples from each participant for bacteria correlated with the absence of S aureus . They found 101 samples positive for bacillus, primarily Bacillus subtilis ( B subtilis ), which is often mixed with other bacteria in probiotic products. The researchers then sampled for S aureus and found 25 positive gut samples and 26 positive nose samples. Strikingly, the researchers say, they found no S aureus in any of the samples that contained bacillus.
Using chromatography and mass spectrometry, the study team identified fengycins—a class of lipopeptides—as the specific bacillus substance that inhibited the S aureus sensing system. Other tests showed that fengycins had the same effect on several different strains of S aureus , including high-risk USA300 methicillin-resistant S aureus (MRSA).
To further validate their findings, the researchers colonized the gut of mice with S aureus and fed them B subtilis spores. Probiotic bacillus given every 2 days eliminated S aureus . The same test using bacillus where fengycin production had been removed had no effect: S aureus grew as expected.