What causes antibiotic resistance?

Bacteria are becoming increasingly resistant to the antibiotics we use to treat disease.

Antibiotic resistance is a good example of natural selection. Exposure to antibiotics increases selective pressure in bacterial populations, resulting in an increased percentage of resistant bacteria, with new bacterial generations inheriting resistance genes. Bacteria can sometimes pass on resistance by sharing genetic material with each other. They can also become resistant after spontaneous changes to their genes. Certain genetic mutations allow bacteria to produce enzymes that inactivate antibiotics. Others change their external composition so that antibiotics cannot reach it. Some bacteria even develop infusion mechanisms to flush out antibiotics. The overuse and misuse of antibiotics has exacerbated the problem of antibiotic resistance.