Since bacteria becomes resistant to antibiotics after an unfinished course, is it possible to do anything to be able to get treatment with the same antibiotic again, and reverse the resistance in the bacteria?

Or, the bacteria with the resistance will stay resistant forever (until death)?


There are some websites that are claiming that some natural remedies might be effective, like taking "Honey", which doesn't seem to be medical facts.

  • $\begingroup$ @Sancho I have edited my question, and added that some sites claims that it is possible. $\endgroup$
    – sharp12345
    Apr 6, 2013 at 18:56
  • $\begingroup$ To confirm, is the claim: "It is possible to make bacteria vulnerable to antibiotics that they are currently resistant to" $\endgroup$
    – Sancho
    Apr 6, 2013 at 18:59
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    $\begingroup$ @Sancho , Yes, that is it exactly, the title of the question has been edited (by wertliq) to say that. $\endgroup$
    – sharp12345
    Apr 6, 2013 at 19:33
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    $\begingroup$ I think you may be starting from a misconception. Each individual bacteria has a fixed level of resistance that generally doesn't change throughout its life. Antibiotics easily kill those that are less resistant, leaving behind the more resistant bacteria to spread. There is no resistance that was "gained" by any individual bacteria, so nothing to reverse. A better summary of your linked question would be "bacterial populations become resistant" rather than "bacteria become resistant". This might not change what your question is, but wanted to point this out. $\endgroup$
    – Sancho
    Apr 6, 2013 at 22:11
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    $\begingroup$ What would make this much clearer is a link to a notable source that makes the claim you're questioning... then we'll be able to pin down exactly what is meant and get a good answer for you. $\endgroup$
    – Sancho
    Apr 6, 2013 at 22:12

3 Answers 3


Perhaps it is useful to first consider how resistance is gained:

If you treat a population of bacteria with an antibiotic, some may die and some may live.

If none die, they are obviously resistant.

If all of them die, then all of them were sensitive, meaning that the size of the population and the variation were not large enough in order for some of the bacteria to be resistant. One approach would be to try to get larger genetic variation by inducing mutations with some mutagen. In addition, you can take a larger population. This would in effect let you sample a larger part of the genetic space to see if you can find a resistant strain. Of course it is possible that this will not work.

If some die and some are resistant, the situation is slightly more complicated. One possibility is that those which lived are genetically resistant (their DNA is different). To see if this is the case, you take those which lived and treat them again with the antibiotic. If they all live, they are resistant. Another possibility is that they are scholastically resistant. This phenomenon is known as bacterial persistence. What happens is that there is a genetic switch that randomly bestows resistance in some fraction of the population, let's say 10 percent. If you now take this population and reapply the antibiotic, only 10% of the population will survive. This interesting mechanism allows the bacteria adapt more quickly, since they do not have to make modifications to their DNA.

I am guessing that if the bacteria are genetically resistant, they will stay resistant. If the bacteria are scholastically resistant, it might be possible to affect the genetic switch which causes the persistence. This, in addition to reducing the size of the population, might cause a situation where none of the bacteria in the population are resistant long enough to survive.

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    $\begingroup$ You've explained how bacterial resistance develops, but you haven't explained how it might go away (except an allusion in your description of bacterial persistence). $\endgroup$
    – blep
    Apr 7, 2013 at 19:03
  • $\begingroup$ @dd3 Sorry about that, I misread the question. I will edit it slightly and will keep it just since it might be useful for someone. $\endgroup$
    – Bitwise
    Apr 8, 2013 at 1:34
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    $\begingroup$ Just an addition to the above answer........ In cases where resistance is because of overexpression of a certain gene such as an efflux pump, because of promoter mutations, the WT will outcompete the mutant because of the latter's additional cost of gene synthesis. In cases where a receptor mutation causes insensitivity to a drug then perhaps the mutant may underperform in processes where the receptor is vital. And WT can outcompete the mutant. If there is no trade-off for a mutation then it wont go away $\endgroup$
    Apr 8, 2013 at 16:20

Bitwise has explained how antibiotic resistance develops in bacteria. To address how it might go away: as long as the antibiotic is around, there is selective pressure on the bacteria to preserve the parts of their genome that confer antibiotic resistance. If, for example, some bacteria developed mutations that made them no longer antibiotic-resistant, these bacteria would die, and thus, only the antibiotic-resistant bacteria would reproduce.

For antibiotic-susceptible bacteria to develop and persist, you'd need to take away this selective pressure (no more of the antibiotic around to kill the antibiotic-susceptible bacteria) so that there would be no particular advantage to carrying non-mutated copies of the antibiotic-resistance gene(s). Of course, the natural rate of mutation is not that high, so I think it would take time for antibiotic-susceptible bacteria to reappear (unless there was a mutagen around).

EDIT: antibiotic-susceptible bacteria would become more prevalent if there was a way to select for them, over antibiotic-resistant bacteria. For example, if there were conditions under which maintaining antibiotic-resistance genes becomes unfavorable, antibiotic-susceptible bacteria would reproduce more often/faster (see the term fitness), and thus become more prevalent. However, this does not change the mutation rate - only selects for things that have already evolved.


The other answers describe the situation well for an individual, however there have been cases in the past where antibiotic resistance has emerged and been outgunned by medical advances to overcome this specific resistance. A good example of this co-amoxyclav.

The original Amoxicillin, a β-lactam antibiotic, was previously effective against a good range of bacteria. However antibiotic resistance then developed when some bacteria began producing β-lactamase, an enzyme which degraded the β-lactam ring rendering the drug (and all within its class) useless against them.

This resistance was then countered when a way to inhibit the β-lactamase the bacteria were producing was discovered. Clavulanic acid does this, leading to the mixture of its potassium salt with Amoxicillin. The mixture (coamoxyclav) allows the amoxicillin to still be effective against the previously resistant bacteria, as the resistance they have been developed is being inhibited in parallel.

For this reason in a hospital setting it is more common to prescribe Co-amoxyclav rather than a beta-lactam antibiotic in isolation.


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