Antibiotic-Induced Changes in the
Intestinal Microbiota and Disease
The gut microbiota contains trillions of bacteria belonging to hundreds, possibly thousands, of species and is crucial for optimal maintenance of host physiological processes. The microbiota protects against infections and other pathologies by directly inhibiting invading microbes or by orchestrating appropriate immune responses; conversely, metabolites produced by some gut commensals can promote a variety of diseases such as atherosclerosis or cancer. Antibiotics alter the microbiota composition, resulting in an increased risk of disease, secondary infections, allergy, and obesity. In addition, they promote the spread of drug-resistant pathogens, making the search for alternative clinical approaches imperative. Novel strategies are being developed to substitute or complement antibiotic therapies, attempting either to selectively target pathogens without perturbing the microbiota and/or to reestablish commensal communities together with the protective and bene- ficial effects they confer to the host.