Skepchick Quickies – Weekend Edition, 5.24


Jen is a writer and web designer/developer in Columbus, Ohio. She spends too much time on Twitter at @antiheroine.

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  1. I sent this to my Dad, who has run an ER/ICU (leaving the name out for confidentiality). There is one thing that doesn’t make sense. Dr. Meisel says that the infection could either be by bacteria, virus, or possibly not be an infection at all. He says that if there is no bacteria, then giving antibiotics may cause the development of antibiotics resistant strains, but how could this happen without the microbe being in the body? There appears to be something missing in the line of reasoning.

  2. except…you are full of OTHER bacteria, and they can be selected for antibiotic resistance.

    Bacteria have the ability to swap DNA bits easily, and are not restricted by species. So it’s quite possible/likely that a plasmid swap with a harmless bacteria could share the resistance.

  3. jreedgt:
    the antibiotic resistant strains could be bacteria living in her body that are not necessarily causing the infection but because antibiotics aren’t very discriminant in their killing, these other potentially infectious bacteria could develop a resistance. I’m not a doctor or anything, but this is what i have come to understand after working in a hospital for a while.

  4. Here are is the answer:
    When we take antibiotics orally, it doesn’t all get into the bloodstream immediately. Instead, it mixes with our intestinal contents before getting absorbed, and some of it doesn’t get absorbed.

    What also lives throughout the lumen of our 30-40 foot long intestinal tract are bacteria: hundreds of different species in concentrations of up to 10^11 (yes, 100,000,000,000) organisms per gram of stool. So if you have over two pounds of stool working its way through your intestinal tract, you could easily have over a trillion bacteria in your gut’s lumen.

    Those bacteria will not be exposed to a lethal dose of the antibiotic. Some may already be resistant to it due to its mechanism of action not being effective for that particular strain. Others will be exposed to such dilute concentrations that bacteria that do possess some mechanisms for growth in the presence of dilute antibiotiic concentrations will find survival advantage. These selected organisms then become the dominant population, as all the other more sensitive bacteria will be killed. As a result, the survival rewards of having resistance mechanisms get disseminated.

    We can reproduce this in the laboratory with serial passage of bacteria in the presence of various dilutions of antibiotics. As reincubation of selected bacteria in antibiotic dilutions continues, you can see strains growing in higher and higher concentrations of antibiotics. The definition of resistance is dependent on a bacterial strain’s minimal inhibitory antibiotic concentration exceed the antibiotic concentrations achieved in plasma following a standard antibiotic dose in a physiologically normal human.

    Note: I’m not a doctor, but an engineering Ph.D. student. I know that bacteria are within the body at all times (some harmful – see E coli). However, this is an example of a very important piece of information that was left out in the explanation that needs to be said for us “laymans.”

  5. …so, say you take antibiotics for something like strep. Will they also kill the delicate bowel bacteria?(I can’t imagine that it would only target the undesirable). How do you get the good, delicate bacteria back? Kefir?

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