Should you take a probiotic with your antibiotic?

We are not one organism, we are many organisms. And when we disturb the relationship with our symbiotic partners, we can suffer unpleasant and sometimes life-threatening consequences. One of the most fascinating areas of medical research is the study of how our bodies interact with the the various organisms that we carry around, on us and in us. A focus is the gastrointestinal tract, particularly how the composition and function of those organisms contribute to what we think of as “normal” function, and how they can affect our risk for obesity and disease. My favorite analogy is from Science Based Medicine’s Mark Crislip who likens it to a “metaphorical rainforest” giving a vivid mental image of the of the number of species (thousands) in our guts, and the complexity of that ecology. If the gastrointestinal tract is a rainforest, then antibiotics are the metaphorical clear cutters, wiping out some of the normal bacteria, and creating the conditions where unwanted bacteria can grow.

Antibiotics are among the most useful (if not the most useful) classes of drugs in widespread use today. They’re also among the most widely prescribed, and both antibiotic overuse and their addition to animal feed present real dangers to their ongoing effectiveness. Their popularity stems in part from their effectiveness, but also from the perception that they are safe. And, in general, a course of most antibiotics is usually well tolerated. Among the side effects, diarrhea is common (with an incidence of 5% to 39%). It’s due in part to the antibiotic killing off our normal “good” bacteria, which can significantly change the most prevalent species. In some cases, “bad” bacteria can surge as a result. Clostridium difficile infection is pretty much the worst gastrointestinal consequence of antibiotic therapy. It isn’t just a cause of antibiotic-induced diarrhea, “C. diff” infections are virulent and vicious, spreading easily, especially among hospitalized patients, causing widespread misery and even killing.