Medicine: Evolution of bacteria and drug resistance

Contributed by paustian on Sep 21, 2016 - 11:51 AM

This frightening experiment demonstrates how important it is that we manage our antibiotics carefully and avoid overuse. A giant bacterial growth chamber was created. The bottom layer was solid medium, and the top was a semi-solid medium that bacteria could swim through. The edges of the chamber had no antibiotics, while an area adjacent has a dose that would normally kill a typical strain of E. coli. Next to that area, was a third that had 10x a lethal dose, next to that 100x a lethal does, and finally in the middle of the chamber 1000x a lethal dose. Go watch the video and see what happens.

This experiment demonstrates two important concepts.

  1. Bacteria evolve in the presence of strong selective pressure, and they do it very quickly
  2. No matter the antibiotic we synthesize or discover, microbes will eventually develop resistance to it.

I will leave you with one slightly comforting thought. In this experiment, there was a huge reward to the E. coli strain for developing resistance to the antibiotic, an entire new area of the plate was now available for growth. There was also no downside. If the changes in its DNA that made it resistant had deleterious effects, for example, causing you to grow more slowly or changing membrane permeability, that was not a problem because there was no other competing organisms present and you are in a rich medium environment. In a medical situation where you are treating a patient, the immune system will be present and destroying microbes, probably gaining the upper had on a slower growing pathogen. Or if the membrane permeability of the bacterium, changes to slow down absorption of the antibiotic, this may also make transport of nutrients into the microbe more difficult. In the rich, forgiving environment of the experimental chamber, it might be able to survive, but in the openly hostile environment of the body, maybe not.