The phenomenon of antimicrobial resistance caused by overuse of antibiotics was predicted as early as 1945 by Alexander Fleming who said "The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily under-dose himself and by exposing his microbes to nonlethal quantities of the drug make them resistant."

Source: https://en.wikipedia.org/wiki/Antimicrobial_resistance#History

Obviously quotes from the history section are hardly authoritative, but I just wanted to check that although his prediction was correct, the mechanism that caused it was misunderstood at that time? My own understanding would be that resistance is about random bacteria being resistant and those bacteria thriving because all other bacteria were killed.


1 Answer 1


In a 2017 analysis in The BMJ, Martin Llewelyn and colleagues addressed the question of whether it is good to advise people prescribed antibiotics to "finish the course".1 I've copied their key takeaways below, but I encourage you to read the full article as they present a convincing argument that overtreatment is more dangerous than undertreatment in regards to the emergence of resistant organisms.

  • Patients are put at unnecessary risk from antibiotic resistance when treatment is given for longer than necessary, not when it is stopped early
  • For common bacterial infections no evidence exists that stopping antibiotic treatment early increases a patient’s risk of resistant infection
  • Antibiotics are a precious and finite natural resource which should be conserved by tailoring treatment duration for individual patients
  • Clinical trials are required to determine the most effective strategies for optimising duration of antibiotic treatment


  1. Llewelyn MJ, Fitzpatrick JM, Darwin E, SarahTonkin-Crine, Gorton C, Paul J, Peto TEA, Yardley L, Hopkins S, Walker AS. The antibiotic course has had its day. BMJ. 2017 Jul 26;358:j3418.
  • $\begingroup$ You have to either subscribe (157 dollars per year) or buy the individual article (£30 / $37 / €33 (excludes VAT)) to read it in full. Regarding 'finishing the course'. Can we trust our doctors to prescribe a course that is commensurate with the illness the antibiotic is designed to treat? If so we should finish the course. If not, how do we decide when to stop? When we feel better? I recently had an abscess on my gums (ew). By day 3 (of a 7 day course) the pain had disappeared. Would it have been a good idea to stop then? $\endgroup$
    – Naj
    Dec 14, 2021 at 18:57
  • $\begingroup$ @Naj -- Here's a PDF hosted elsewhere. My answer addresses the question of antibiotic use in regards to antibiotic resistance, not in regards to disease treatment. Always take your medication as it is prescribed. $\endgroup$
    – acvill
    Dec 14, 2021 at 19:08
  • $\begingroup$ Hi, thanks, read the PDF. Of course, I acknowledge that your answer is about antibiotic resistance. However, the linked article does say the following (addressing my concerns about how you know when you're actually cured, as opposed to just 'feeling better') : "Outside hospital, where repeated testing may not be feasible, patients might be best advised to stop treatment when they feel better, in direct contradiction of WHO advice." and "Research is needed to determine the most appropriate simple alternative messages, such as stop when you feel better." $\endgroup$
    – Naj
    Dec 15, 2021 at 8:23

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