By Saey, Tina Hesman
Science News , Vol. 179, No. 8
Taking unnecessary antibiotics could make the flu or other viral infections worse, a new study suggests.
Mice on antibiotics can't fight the flu as well as mice that haven't taken the drugs, a team from Yale says. Antibiotics quash the immune system's infection-fighting power by killing friendly bacteria living in the intestines, the researchers report online March 14 in the Proceedings of the National Academy of Sciences. These friendly, or "commensal," bacteria help defend against viruses by keeping the immune system on alert for viral invaders, the team discovered.
"There's a lot of beneficial effects of having commensal bacteria," says Akiko Iwasaki, a Yale University immunologist who led the study. "This is one that was unexpected, but makes sense."
Scientists knew that friendly bacteria in the intestines could help stop disease-causing bacteria from setting up shop in the gut. And previous experiments hinted that gut microbes could influence how well the immune system works, but researchers thought the effect was mainly confined to the digestive system and wouldn't show up in far-away tissues such as the lungs. "What's fascinating about [the new study] is that there's a distant regulation of resistance to viruses by gut microbiota," says Alexander Chervonsky, an immunologist at the University of Chicago.
Lungs are normally sterile, so it was a bit of a surprise that killing bacteria in the colon would have an effect on how well the respiratory system could fight viruses. …