3 ms·

Resistance against antibiotics cannot come free for bacteria. If we stop using some, the resistance should vanish as quickly as it turned up, shouldn't it?

• postexitus 3y ago
  It's not like it's some mechanism that they "fight" against the antibiotics. Once their protein structure has evolved (naturally selected under external pressure), it comes for free. Now remove the antibiotics, they will start diverging from the "resistance" yes, but the baseline will be "resistant" and as soon as you re-introduce the same antibiotic back, they will become the dominant strain. The only way to prevent this is to make sure they never become the dominant strain under selection pressure - although it's too late for most of the cases.
  • zdragnar 3y ago
    Not quite. Often an evolutionary change may come at a cost to fitness under circumstances that differ from the current environment. As such, once the antibiotics are stopped, non-resistant bacteria may be better able to compete for resources and multiply. There's a reason super resistant strains are most commonly found in hospital and health care settings: https://www.cdc.gov/drugresistance/biggest-threats.html https://www.cdc.gov/drugresistance/biggest-threats.html If the ongoing cost of the mutation was truly free, one would expect it to spread out beyond these places more prominently. Edit: I may have under-emphasized that there is no guarantee, and we shouldn't rely on this property.