How Does Drug Resistance Evolve?
When you take antibiotics for a bacterial infection, billions of bacteria may be killed right away. However, there are likely to be a few that survive. Antibiotics kill the less resistant bacteria, leaving behind the more resistant bacteria to survive and reproduce. When resistant bacteria reproduce, the genes that make them resistant are passed on to their offspring; and bacteria reproduce rapidly. In six hours, one cell can produce as many as 500,000 offspring. In addition to their ability to reproduce quickly, populations of bacteria evolve rapidly through another process as well. Bacteria use plasmids—small loops of DNA—to transfer genetic material between individual cells. This transfer of plasmids between cells is called conjugation. Some plasmids pass on resistance for one particular antibiotic. Others can transfer resistance for several antibiotics at once. What characteristics do resistant bacteria pass on to their offspring? Some have cell walls that antibiotics cannot easily
