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Antibacterial-resistant strain

  1. Oct 6, 2005 #1


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    Humm.. I actually have a biology question. I don't normally troll around in this part of PF, so I don't know if it has been asked before.

    There have been advice to not use antibacterial soaps, and reducing the frequency of use of antibiotics. The reason for this is the report on the more frequent discovery of strains of bacteria that are resistant to antibiotics.

    My question is, what is the connection between these two?

    From my understanding of how evolutionary process occurs, you have mutant strains of a particular species occuring randomly. Thus, presumably antibiotic-resistant strain would occur no matter if one uses antibacterial soaps or antibiotics. So why would using these things promote their "existence"? It is because the antibiotics kill the existing bacterial strains and thus, there's less competition for "food" for the resistant strain?

  2. jcsd
  3. Oct 6, 2005 #2
    Yes. Imagine your skin is covered with bacteria (it is) and 99.99% of those bacteria are beneficial. The antibacterial soap kills these beneficial bacteria along with "germs" (which are not very numerous on your skin to begin with, compared to beneficial microbes.) The ones that don't get killed by the soap. are the antibiotic resistant germs - a small sub population of the germs, occuring naturally.

    So now you've killed off the antibiotic sensistive beneficial bacteria, the antibiotic sensitive "germs," and left only antibiotic resistant bacteria (some of those being germs) behind. They can take over the joint.

    It's like how your lawn is mostly grass, with a few weeds. The grass (good guys) help to keep the weeds from taking over. If you kill the grass, the weeds can spread like crazy through your property.

    The other concern is that the antibiotic resistance can *spread* to other bacteria. The more of that sort of bacteria that's around, the more likely it will be able to spread into some other germ, and make that germ harder to treat.
    Last edited: Oct 6, 2005
  4. Oct 6, 2005 #3


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    Just to expand upon Patty's comment regarding the "spread" of antibiotic resistance...this occurs via a process known as bacterial conjugation where two bacteria can transfer plasmid DNA between one another (this is something separate from the chromosomal DNA), and these plasmids are what carry antibiotic resistance.

    Here's one site that explains a bit about bacterial conjugation:

    And an animation that illustrates it:

    So, if you kill off most of the non-harmful and non-resistant bacteria, that leaves more of the resistant bacteria around to spread the resistance to what were previously non-resistant bacteria in addition to allowing the resistant bacteria to multiply disproportionately to the non-resistant bacteria.
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