'Good' Bacteria Keep Immune System Primed to Fight Future Infections

Scientists have long pondered the seeming contradiction that taking broad-spectrum antibiotics over a long period of time can lead to severe secondary bacterial infections. Now researchers from the University of Pennsylvania School of Medicine may have figured out why. The investigators show that "good" bacteria in the gut keep the immune system primed to more effectively fight infection from invading pathogenic bacteria. Altering the intricate dynamic between resident and foreign bacteria -- via antibiotics, for example -- compromises an animal's immune response, specifically, the function of white blood cells called neutrophils.

Senior author Jeffrey Weiser, MD, professor of Microbiology and Pediatrics, likens these findings to starting a car: It's much easier to start moving if a car is idling than if its engine is cold. Similarly, if the immune system is already warmed up, it can better cope with pathogenic invaders. The implication of these initial findings in animals, he says, is that prolonged antibiotic use in humans may effectively throttle down the immune system, such that it is no longer at peak efficiency.

"We suggest that if the immune system is on idle, and you treat someone with broad-spectrum antibiotics, then you turn the system off. The system is deprimed and will be less efficient at responding quickly to new infections."

The findings also provide a potential explanation for the benefits of probiotic therapies because keeping your immune system primed by eating foods enhanced with "good" bacteria may help counteract the negative effects of sickness and antibiotics.

Researchers have for many years understood that most bacteria in the body are not "bad." In fact, humans (and mice) have a symbiotic relationship with their resident microbes that significantly impacts, among other things, metabolism and weight homeostasis. The study was funded by the US Public Health Service.

Steve - I love how these researchers are taking credit for finding out why this happens. You and I have know it for years!