3 ms·

It is not. Basically it says: "bacteria will get resistant with prolonged exposure, but lose resistance when they are no longer exposed."

• piratelax40 10y ago
  be very careful about semantics, the statement is: bacteria will become resistant overtime when exposed to antibotics at concentrations insufficient to kill all of them, however when removing the selective pressure of antibiotics, they will "lose" resistance as that selective pressure is no longer applied. As the poster above mentioned, energetically, resistance to antibiotics is costly, as bacteria will do things like increase the number of efflux pumps in their cell membranes pumping out antibiotics. When there are plenty of nutrients available as other strains have died, this is an acceptable tradeoff, however without that pressure, the strains with less defense mechanisms, but also need less nutrients to survive, will again outcompete and become dominant. Finally, just to reiterate, it is exposure at levels not high enough to kill all strains that causes resistance development. If you maintain concentrations so high that no strains can survive, resistance will never develop. Unfortunately, this is virtually impossible in practice, as adverse safety events would also occur too frequently at those 'scorched earth' levels.