Even if you’ve been blessed with the constitution of an ox, you’re likely to have been handed a prescription for antibiotics at some stage in your life. And you’ve probably felt better for taking them. But going on a lengthy course of broad-spectrum antibiotics can bring problems of its own. While the initial problem may clear up, taking the antibiotics can mean you become more prone to severe secondary infections.

For a long time scientists have been wondering why taking a medication that knocks one infection out, invites others in. Now research from the University of Pennsylvania School of Medicine may have given us an explanation.

The research has shown that the good bacteria in the gut keep the immune system at the ready to fight off infection from invading pathogenic or disease-causing bacteria. For senior author Jeffrey Weiser, MD, professor of Microbiology and Pediatrics, it’s rather like starting a car: It’s much easier to start moving if a car is idling than if its engine is cold. In the same way, if the immune system is already warmed up, it can better cope with the bad bacterial 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, so that it is no longer working at peak levels.

It’s down to white blood cells known as neutrophils, and how well they’re working. “Neutrophils are being primed by innate bacterial signals, so they are ready to go if a microbe invades the body,” Jeffrey Weiser explains. “They are sort of ‘idling’, and the baseline system is already turned on.”

Antibiotics

“One of the complications of antibiotic therapy is secondary infection,” says Jeffrey Weiser . “This is a huge problem in hospitals, but there hasn’t been a mechanistic understanding of how that occurs. 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 study was carried out with mice, so further research needs to be done, but findings so far show that it may be possible to find a way of giving antibiotics to humans with just the beneficial effects and not the drawbacks.

So how do you keep the immune system ready to fight off infection if you have to take antibiotics? The first step is to live well before you need medical treatment. “Try to stay as healthy as possible,” says dietitian Sian Porter, spokesperson for the British Dietetic Association (BDA). “Stay physically active, get enough sleep and have a good diet. If you’re eating plenty of different types of fruit and vegetables, oily fish, whole grains and calcium, this should help to keep you healthy.”

Sometimes though, even this isn’t enough to keep us well and antibiotic-free. Elizabeth Weichselbaum, of the British Nutrition Foundation, has carried out a study of research into probiotics and how well they work. Probiotics are designed to provide us with good bacteria and help recreate balance in the gastro-intestinal tract.

“They aren’t wonder pills, but they can help in some areas,” she explains. “When I was working on the review I found that a lot of people develop diarrhoea when they take antibiotics – this is because they kill off the good bacteria in your gut. I also found quite good evidence that some strains – Lactobacillus casei GG and saccharomyces boulardii – performed well. So it can be useful when you take antibiotics to take some probiotics as well, specifically to reduce your chances of developing diarrhoea.”