How did bacteria become resistant?

We all know that antibiotic resistance increases through improper use of antibiotics. With recent discoveries of bacteria containing antibiotic resistance genes in isolated tribes it would seem that bacteria have always been resistant- so why is it such a problem now?Bacteria, like all organisms, evolve. Through improper use of antibiotics we have changed the course of this evolution away from natural selection towards selecting bacteria which contain the genes for resistance. Humanity has selected out the strongest, most resistant bacteria and that what we are trying to fight off today.

Over the last 60 or so years antibiotic production has gotten faster, easier and cheaper resulting in millions of tons of antibiotics in the environment. This has provided a strong evolutionary push towards resistant strains. Additionally bacteria are able to share genes for antibiotic resistance between themselves using ‘plasmid exchange’. It appears gene sharing is particularly common in S. aureus species.

There are many other ways bacteria become resistant to antibiotics which make this problem more complicated. The only way for certain to reduce the evolutionary pressure for bacteria to contain these genes is to reduce the amount of antibiotics bacteria are exposed to.

For more information see this informative review in Microbiology and Molecular Biology Reviews.

For a detailed explanation for plasmid exchange click here

Picture shows plasmid exchange under an electron microscope.

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