Be a good landlord.

Antibiotic-resistant superbugs are scary, but they are not the only negative, long-term consequence of our overuse of antibiotics. Dr. Martin Blaser of the Department of Medicine at NYU recently wrote commentary for Nature regarding the liberal use of antibiotics and its destructive impact on beneficial bacteria. Our gastrointestinal tracts provide habitat for a community of microorganisms that aid in digestion, produce vitamin K, and guard against harmful invaders. From an ecological perspective, these are mutualisms – relationships in which both organisms, the human and the bacterium, derive a benefit. This relationship should be protected. Instead, we cause irreparable damage the community of helpful bacteria with repeated courses of antibiotics. A therapeutic dose of amoxicillin may clear-up an ear infection, but not without collateral damage to these beneficial microbiota. Many people experience an upset stomach during a course of antibiotics. This is an indication that our helpful bacteria have been eliminated, but the results may go far beyond a tummy ache.

I spent some time in the Blaser Lab this summer where scientists and students were hard at work researching Helicobacter pylori. As Dr. Blaser explains in his essay, H. pylori was the dominant microbe in the stomachs of most people in the twentieth century. By the turn of the twenty-first century, however, fewer than 6% of children in the United States, Germany and Sweden were carrying the organism. H. pylori may have a bad rap for its connection to ulcers and stomach cancer, but its eradication has several surprising effects. For instance, people without the bacterium are more likely to develop asthma, hay fever, and skin allergies. Moreover, H. pylori helps regulate ghrelin and leptin, hormones that control appetite and metabolism, which may have implications in obesity. A dose of amoxicillin administered to treat a respiratory infection will also eliminate H. pylori in 20 – 50% of cases.

Farmers have noticed that repeated low doses of antibiotics cause animals to gain weight with less food. The Blaser lab has discovered that comparable sub-therapeutic doses cause changes in body fat and tissue composition in mice. Large doses, like those used to treat childhood infections, have similar results. Dr. Blaser goes on to emphasize the importance of age. The physiological changes that are triggered by antibiotic usage early in life are the hardest to reverse, yet the average child in the United States receives 10 – 20 courses of antibiotics before age 18.

To read more about threats to your friendly bacterial tenants and what we should do to protect them, read Dr. Blaser’s expert opinion in his essay for Nature.