Thursday, March 17, 2011

Gut Bacteria helps fight Influenza and Lung Disease

Bacteria have their place. They are not always bad and sometimes they are beneficial.

They aid in digestion, help keep our intestines harmoniously balanced, and are even important in diabetes, obesity, and inflammatory bowel disease.

But what about beyond our gut? Scientists found that bacteria can avert the flu by keeping the immune system on alert for seasonal viral intruders.

Mice on antibiotics can’t fight the flu as well as mice that haven’t taken the drugs, researchers say.

Antibiotics quash the immune system’s infection-fighting power by killing friendly bacteria living in the intestines.

For a month, the researchers treated mice with antibiotics commonly given to people with bacterial infections and then they gave them the flu. The treated mice were more susceptible.

Turns out, the naturally-occurring bacteria taken out by antibiotics actually help produce flu-fighters – like immune cells and antibodies that fend off the viral infection.

The gut is where the bulk of the body’s roughly 100 trillion ‘commensal’ – harmless or beneficial – bacteria live [Nature]. And since lungs are normally sterile, it was a bit of a surprise that killing bacteria as far away as the colon would have any effect on how well the lungs could fight viruses [Science News].

“It seems that the commensal bacteria in the gut are providing a crucial signal throughout the body that prepares the body for fighting infection,” says lead author Akiko Iwasaki of Yale. “And it’s probably not only restricted to lungs.”

The findings suggest that long-term use of antibiotics could hamper our ability to fight influenza, Iwasaki says, perhaps even impair the effect of a vaccine.

Additionally, it also implies that our diet affects our ability to fight viruses by influencing the composition of our beneficial bacteria. For example, probiotic treatments, like yogurt, may help stimulate our immune systems during flu season.

The study was published in the Proceedings of the National Academy of Sciences this week.

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