caveBy: Dr. Scott Dee

I recently read a paper published in Nature Communications that reported the recovery of a bacterium that was resistant to 18 different antibiotics, despite being isolated from a cave untouched by the outside world for greater than 4 million years. The bacterium, Paenibacillus sp. was recovered 1000 feet underground in Lechuguilla Cave, a UNESCO World Heritage Site that had been closed to mankind since 1986, outside of the researchers who explore the many natural wonders of caves.

The authors of the paper concluded that the evolutionary pressure to conserve resistance genes in bacteria is strong and has existed for millions of year, long before antibiotics were even available for use in human and animal health.

To me, this makes sense in many ways:

  1. We know that one way antimicrobial resistance (AMR) can occur in bacteria is through constant application of evolutionary pressure, resulting in simple mutations in the genome that promote the “survival of the fittest” and enhance resistance to antibiotics.
  2. This report suggest that bacteria are regularly exposed to antibiotics through the environment, i.e. through the soil, water, etc. As many antibiotics were originally derived from molds and fungi from the soil, this is not surprising.
  3. This report also reinforces that antimicrobial resistance can occur independent of the use of antibiotics in human or animal health.

I think this a breakthrough study that explains the combined role of natural selection and the environment on the development of antimicrobial resistance. Clearly, AMR is not always due to the use of antibiotics in agriculture. While we must always practice the principles of responsible use, those who criticize antimicrobial use in livestock need to have an open mind and not over conclude on the effects of judicious antibiotic use in livestock.

Bottom line: It’s hard to argue with a 4 million year old cave!

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