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I understand bacteria can mutate and develop resistance against antibiotics, but I do not understand how finishing an antibiotics treatment prevents this. In my simple thought process, when an individual bacterium has a mutation with antibiotics resistance, the antibiotics do not work on it. So whether I take 1 antibiotics pill or finish the whole treatment would not kill this bacterium, leaving it able to multiply later.

I am guessing the actual situation is either one of these things:

  • The immune system itself, relieved of pressure by most bacteria being dead, kills the bacteria that developed resistance. Important note here would be that if the immune system is completely shut down, perhaps finishing an antibiotics treatment would actually INCREASE resistance as only the bacteria with resistance would survive. So I suppose this theory is wrong.
  • Even individual bacteria only developed resistance which is not the same as immunity and bombarding it with antibiotics for multiple days still (usually) means that the bacterium dies.

Does that make sense or is there a thing I'm overlooking here?

Sebastiaan van den Broek
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  • You are prescribed enough to ensure that all of them are gotten and if you don’t take the full dose you can’t ensure how many survive and mutate – Joe W Jun 17 '18 at 18:04
  • @JoeW I'm sorry but comments are not for answering the question, and that is not a source-backed answer either, nor does it really explain anything. – Sebastiaan van den Broek Jun 18 '18 at 08:01

1 Answers1

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Mayo Clinic on the example of tuberculosis:

Stopping treatment too soon or skipping doses can allow the bacteria that are still alive to become resistant to those drugs, leading to tuberculosis that is much more dangerous and difficult to treat.

So, the logic behind completing the course is to kill as much bacteria as possible to prevent the surviving ones to mutate and become resistant.

UPDATE: This question seems to be quite complicated, actually.

According to The BMJ (2017):

However, the idea that stopping antibiotic treatment early encourages antibiotic resistance is not supported by evidence, while taking antibiotics for longer than necessary increases the risk of resistance.

The official policies of prescribing antibiotics have not changed because of such discussions, but the BMJ authors recommend that the information material for the public should contain "take antibiotics exactly as prescribed" and not "finishing the course." So, it's a doctor and not a patient who should decide the treatment period.

Jan
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  • *“If you are continuing with antibiotics for too long, the non-resistant pathogenic bacteria and the harmless bacteria (a part of normal body flora) will die thus leaving more room for the antibiotic-resistant bacteria to grow.”*

    But I’m not talking about taking the antibiotics for too long but for the regular prescribed amount of time. This quote shows the reverse of the thing we’re always taught, that not taking all pills for the prescribed period causes antibiotics resistance, while this quote says that is actually caused by taking it too long.

     – Sebastiaan van den Broek Jun 18 '18 at 08:41
  • For the record, I think it makes a lot of sense what you're saying, but as far as I know doctors always hammer on the fact that you finish the treatment, not that you don't take more than advised. And I thought they did this because of resistance. – Sebastiaan van den Broek Jun 18 '18 at 08:45
  • OK; I edited my answer. Let me know if it is too confusing. – Jan Jun 18 '18 at 08:58
  • I see... so only if taking multiple antibiotics it matters that you finish all? Otherwise you could just take 1 and hope your body will be able to deal with the rest of the infection on its own? The whole process seems quite hit-and-miss, especially considering the treatment period for different diseases is different. – Sebastiaan van den Broek Jun 18 '18 at 09:19
  • Yes, a combination of antibiotics is given when the problem with resistancy is already known and expected: in tuberculosis, chronic stomach infection with H. pylori, etc. There are usually years or decades of studies behind finding the right antibiotic combination and the right period to use them for every specific infection. – Jan Jun 18 '18 at 09:28
  • So, the instruction that you must complete the prescribed antibiotic (only one kind) is nothing but making sure the patient complies? – Nobody Jun 18 '18 at 11:03
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    Yes. Some people stop taking antibiotics as soon as they start to feel better. – Jan Jun 18 '18 at 11:06
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    So, the instruction is just some kind of insurance that the antibiotics kills all the bacteria? What if the side effects cause harm? – Nobody Jun 18 '18 at 11:10
  • Antibiotics commonly cause side effects, such as nausea, which can make people to stop taking them. If side effects become unbearable or dangerous (allergic reaction), one should speak with a doctor about what to do. Often, changing the antibiotic helps. – Jan Jun 18 '18 at 11:15
  • Your firs paragraph is simply wrong. The instruction applies regardless of how many antibiotics are being given. – Carey Gregory Jun 18 '18 at 13:17
  • I removed that part, because it's not directly related to the question, anyway. – Jan Jun 18 '18 at 14:26
  • Reading the abstract link, am I right in thinking this us a review of the BMJ article linked? If so the review is basically saying that the BMJ article is only an opinion piece which is only suggesting that not only do we need to finish the course of antibiotics, but we should be mindful that doctors should not over-prescribe. – Chris Rogers Jun 19 '18 at 08:51
  • For their own personal health reasons and for public health reasons such as control of multi resistant bacteria, doctors advice must be followed by the public. Doctors must be trusted to do the right thing. If the prescription was too large in the first place, stopping early can be better than finishing the course for reasons mentioned in the BMJ article. Finishing early when the course length was correct can be detrimental to health. It is a balancing act. – Chris Rogers Jun 19 '18 at 09:01
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    I removed the abstract link from PubMed Health and kept only the original BMJ article. You can say that the BMJ article is only an opinion piece,but this piece says that the current policy to finish the antibiotic course is also just an opinion not supported by evidence. Such discussions, if supported by evidence from future studies may lead to change in the antibiotic prescription policy. – Jan Jun 19 '18 at 09:09