(credit: Global Panorama/Flickr ) In a battle against an infection, antibiotics can bring victory over enemy germs. Yet that war-winning aid can come with significant collateral damage; microbial allies and innocents are killed off, too. Such casualties may be unavoidable in some cases, but a lot of people take antibiotics when they’re not necessary or appropriate. And the toll of antibiotics on a healthy microbiome can, in some places, be serious, a new study suggests. In two randomized, placebo-controlled trials of healthy people, a single course of oral antibiotics altered the composition and diversity of the gut microbiome for months, and in some cases up to a year. Such shifts could clear the way for pathogens, including the deadly Clostridium difficile . Those community changes can also alter microbiome activities, including interacting with the immune system and helping with digestion. Overall, the data, published Tuesday in the journal mBio , suggests that antibiotics may have more side effects than previously thought—at least in the gut. In the mouth, on the other hand, researchers found that microbial communities fared much better, rebounding in weeks after antibiotic treatments. The finding raises the question of why the oral microbiome is less disturbed by drugs. It could simply be because of the way that antibiotics, taken orally, circulate through the body. Or, it could imply that oral microbiomes are innately more resilient, a quality that would be useful to replicate in microbial communities all over the body. Read 6 remaining paragraphs | Comments

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Single course of antibiotics can mess up the gut microbiome for a year