We often think of probiotics as the “good guys” of gut health, tiny allies in yogurt and supplements that keep our digestive systems balanced. But new research in mice shows that some of these so-called helpers might actually open the door to dangerous infections.
A team at North Carolina State University found that two common probiotic strains of Lactobacillus had opposite effects on gut infections. One strain, Lactobacillus acidophilus, made it easier for a dangerous bacterium called Clostridioides difficile to settle in the gut after antibiotics. Meanwhile, another strain, Lactobacillus gasseri Lg-36, did the exact opposite, helping the gut fight off the invader.
The researchers were shocked at how drastically different the two microbes behaved. Matthew Foley, a microbiologist involved in the study, admitted they expected subtle differences but instead discovered that “they were essentially diametrically opposed.”
So, what made the difference?
It turns out that L. gasseri Lg-36 carries extra genes that make antibacterial weapons—tiny peptides that can directly attack C. difficile. Even better, it encouraged the growth of another group of bacteria, Muribaculaceae, which compete with C. difficile for food, starving it out.
By contrast, L. acidophilus may have acted like an unintentional accomplice. Instead of starving the bad bacteria, it broke down proteins into amino acids, exactly the kind of fuel C. difficile loves.
Rodolphe Barrangou, another NC State microbiologist, explained that the results also highlight a bigger point: not every probiotic leaves once it’s gone. Even temporary residents of the gut can leave a lasting mark, suggesting that probiotics may have ripple effects long after they pass through.
But before you rethink every probiotic capsule in your cabinet, there’s a catch. These findings come from mice, and the researchers caution that the results may not directly translate to humans. As Barrangou points out, “Not all probiotics are the same, not all diseases are the same…. Not all outcomes are the same.”
The team hasn’t yet tested combinations of strains that more closely mimic the blends found in store-bought probiotics. And the way a probiotic behaves could depend heavily on whether a person is already healthy or sick, or what other microbes already live in their gut.
For now, the study is a reminder that the world of gut bacteria is far more complicated than a “good vs. bad” story. Sometimes, even our supposed helpers can play a double game.
For more details, refer to this article published in mBio.
Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.
