Perturbation of intestinal microflora.

This paper discusses the effects of antibiotics on the intestinal microflora, focusing on the microbial constituents, their antibiotic sensitivities, and their metabolic activities. Many of these effects relate to therapeutic doses of antibiotics, not to the very small concentrations found as residues in food. The alterations associated with lower levels of antibiotics are generally unknown because they have not been studied. In the 18th century, Augustus Flemming said: "And it is truly wonderful that a substance, the very aspect and odor of which are sufficient to induce an inevitable nausea, should be regarded not merely as a matter of curiosity and study, but held in the highest repute as a unique and most precious treasure for the preservation of health." Such is the philosophy of the many investigators of the intestinal microflora on whose work this article is based.