• Question: How does bacteria develop immunity so quickly?

    Asked by phoebetomaz to Antibiotics on 19 Jun 2014.
    • Photo: Antibiotics Challenge

      Antibiotics Challenge answered on 19 Jun 2014:

      I can think of four reasons why bacteria evolve resistance so very fast (feel free to add more, team!)
      Firstly, there’s so many of them. An infection will involve millions or billions of bacteria – and only one needs to have the right mutation to start a new resistant type. So even if that mutation is quite unlikely, it’ll happen sooner or later.
      Secondly, they reproduce so fast (sometimes every 20 minutes). This means that one resistant mutant can grow to millions in a few hours, so that there’s a chance for even sttronger resistance mutations to occur and build up – each generation is a chance for the bacteria to get better at surviving the antibiotics.
      Thirdly, the selection we place on them is very strong. If you’re on antibiotics all the bacteria in your body are in a life-or-death situation – and life, as Jeff Goldblum put it so memorably, finds a way.
      And lastly bacteria can sometimes swap genes around between species. When that can happen (it’s particularly dangerous in hospitals) it’s very easy for harmful bacteria to pick up resistance.
      -Louise

      A fifth thing to remember is that many of the antibiotics we use are based on natural products produced by things like penicillin moulds to give them an edge in their fight against bacteria for nutrients etc.
      This war between bacteria and their enemies has been going on for millions of years, so a lot of the drug resistance we find in bacteria is the sophisticated product of a very long evolutionary arms race. Not only quick, but very effective!
      – PB

Comments

  • Photo: phoebetomaz

    phoebetomaz commented on :

    Okay thanks but would the bacteria have developed immunity to antibiotics even if we hadn’t used them?

    • Photo: Antibiotics

      Antibiotics commented on :

      Probably not is the answer, bacteria in your gut don’t meet antibiotics unless you put them there.
      However soil bacteria meet antibiotic producing fungi and other competitors all the time, and so they need their antibiotic resistance machinery just to survive. One problem in our field is termed “horizontal gene transfer”, where that soil bacteria can transfer the whole set of genes that encode resistance into another bacteria which grows in you. The result is a bacteria that can live in you in the presence of antibiotics – drug resistance.

    • Photo: Antibiotics

      Antibiotics commented on :

      To add to what was said above about would resistance (immunity) arise if we hadn’t used them in the first place, then for me (and this is a personal opinion – Aled) the answer is no.

      The emergence of antibiotic resistance is a direct result of selection pressure. The antibiotics are killing the bacteria and only those that are not killed and survive will produce progeny that will survive future treatments (this can arise though many different genetic methods). The field is now trying to move away from antibiotics that directly kill the target organism, but instead make it less virulent (that means it is no longer as nasty and harmful as before). If we can do this, then the selection pressure is lessened and in theory, resistance should not occur as quickly.

      Hope that makes sense, if not let us know and I’ll try to clarify.