Antibiotic Resistance: Delaying the Inevitable (2 of 2)

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Applying our knowledge of evolution
Evolutionary theory predicted that bacterial resistance would happen. Given time, heredity, and variation, any living organisms (including bacteria) will evolve when a selective pressure (like an antibiotic) is introduced. But evolutionary theory also gives doctors and patients some specific strategies for delaying even more widespread evolution of antibiotic resistance. These strategies include:

  1. Don’t use antibiotics to treat viral infections.
    Antibiotics kill bacteria, not viruses. If you take antibiotics for a viral infection (like a cold or the flu), you will not kill the viruses, but you will introduce a selective pressure on bacteria in your body, inadvertently selecting for antibiotic-resistant bacteria. Basically, you want your bacteria to be “antibiotic virgins,” so that if they someday get out of hand and cause an infection that your immune system can’t handle, they can be killed by a readily available antibiotic.

  2. Selecting for antibiotic-resistant bacteriaAvoid mild doses of antibiotics over long time periods.
    If an infection needs to be controlled with antibiotics, a short-term, high-dosage prescription is preferable. This is because you want to kill all of the illness-causing bacteria, leaving no bacterial survivors. Any bacteria that survive a mild dose are likely to be somewhat resistant. Basically, if you are going to introduce a selective pressure (antibiotics), make it so strong that you cause the extinction of the illness-causing bacteria in the host and not their evolution into resistant forms.

  3. When treating a bacterial infection with antibiotics, take all your pills.
    Just as mild doses can breed resistance, an incomplete regimen of antibiotics can let bacteria survive and adapt. If you are going to introduce a selective pressure (antibiotics), make it a really strong one and a long enough one to cause the extinction of the illness-causing bacteria and not their evolution.

  4. Use a combination of drugs to treat a bacterial infection.
    If one particular drug doesn’t help with a bacterial infection, you may be dealing with a resistant strain. Giving a stronger dose of the same antibiotic just increases the strength of the same selective pressure—and may even cause the evolution of a “super-resistant” strain. Instead, you might want to try an entirely different antibiotic that the bacteria have never encountered before. This new and different selective pressure might do a better job of causing their extinction, not their evolution.

  5. Reduce or eliminate the “preventive” use of antibiotics on livestock and crops.
    Unnecessary use of antibiotics for agricultural and livestock purposes may lead to the evolution of resistant strains. Later, these strains will not be able to be controlled by antibiotics when it really is necessary. Preventive use of antibiotics on livestock and crops can also introduce antibiotics into the bodies of the humans who eat them.

Ultimately, recognizing bacteria as evolving entities and understanding their evolution should help us to control that evolution, allowing us to prolong the useful lifespan of antibiotics.

Teach this!
Lesson plans for teaching about the evolution of antibiotic resistance


Learn what you can do to help combat antibiotic resistance at pbs.org.

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