Scientist - News - 06-12-2008:
«BackAntibiotics have a long-term effect on our gut microbiota Beintema, Nienke A recent study shows that a commonly prescribed antibiotic changes the abundance of thirty percent of the bacterial taxa in the gut. The effect last for several weeks, and some taxa fail to recover within six months. The authors conclude that antibiotics may have negative health effects that are yet to be discovered. Although doctors in the Netherlands are more reserved when it comes to prescribing antibiotics than their colleagues in many other countries, the use of antibiotics in medical practice is becoming increasingly common. Many have pointed to the associated risk of antibiotics resistance, but another problem may be lurking under the surface, with potentially far-reaching health implications. Les Dethlefsen and colleagues from Stanford University published a study in the November issue of Public Library of Science (PLoS) Biology that showed the pervasive effects on our gut microbiota of ciprofloxacin, an antibiotic often prescribed against urinary tract infections. The researchers compared the composition of the microbial flora of three healthy persons before and after antibiotic treatment. Ciprofloxacin influenced the abundance of about a third of the bacterial taxa in the gut, decreasing the taxonomic richness, diversity, and evenness of the bacterial community. Gene sequencing In all three individuals, it took around four weeks for the bacterial community to closely resemble its pretreatment state, and several taxa were still not recovered after six months. "These pervasive effects of ciprofloxacin on community composition contrast with prior assumptions of only modest effects of ciprofloxacin on the intestinal microbiota," write the authors in their paper. The effect of antibiotics on gut microbiota had been previously studied, but only with conventional techniques of cultivating microbiota in a laboratory. However, many of the human gut bacteria cannot be cultured and thus have not yet been described. Less than an estimated 20-40% of the microbes in the human gut have so far been cultured. The Stanford researchers, on the other hand, characterized microbial populations by gene sequencing. They focused on short, hypervariable regions of one common microbial gene, the 16S rRNA gene. This technique, called pyrosequencing, is much more discriminative than traditional culturing methods and allows researchers to identify far more bacterial taxa. This study, for instance, confirmed the existence of more than 5,600 bacterial taxa in the human gut, exceeding earlier predictions made on the basis of conventional techniques. Moreover, pyrosequencing is more cost-effective. The result on the pervasive effects of ciprofloxacin, as Dethlefsen and his colleagues point out, may send off a signal to medical practice. As more knowledge becomes available on the relationship between our gut microbial flora and our immune system, as well as diseases such as obesity and diabetes, the Stanford research underlines the need for caution with any treatment that affects the bacterial composition of our gut. More information: PLoS Biology paper of Dethlefsen and colleagues from Standford University Analytic paper on this study in PLoS Biology |