Over at Evolgen, RPM notes an interesting study in PNAS, looking at antibiotic use and how it serves to drive the emergence and maintenance of antibiotic-resistant strains. The current paradigm for antibiotic use is to prescribe relatively high doses of drugs for a few days to a few weeks (or months, in the case of tuberculosis), and patients are cautioned to stay on them until all the doses are finished. However, the new study RPM describes suggests this may be doing more harm than good, looking at what happens with Plasmodium species treated with antimalarials in a mouse model.

Do their results overturn the paradigm? I’m not convinced. First, RPM states that antibiotic resistance is a dichotomy: either sensitive, or resistant strains. But that’s not the case–those are simply the extremes of the spectrum, with many organisms that are some shade of partially resistant to various antibiotics. (For example, while penicillin resistance is rare in Streptococcus pyogenes, it takes much higher doses of the drug to kill them today than it did, say, 40 years ago; they have “intermediate” resistance or susceptibility). As noted in the comments, it’s not only the fully resistant organisms we’re worried about when it comes to antibiotic resistance: it’s also those for which it takes a lot of the drugs to kill, but they’ll die eventually (or at least, the drugs will inhibit their growth). This study doesn’t take those into account, which is a limitation–but then again, it seems designed to be more of a paper to get fellow scientists thinking about these ideas in general, rather than an exhaustive test of every potential hypothesis stemming from them.

Either way, antibiotic resistance is certainly a huge problem, and we need to find better ways to preserve the drugs we do have. Reducing their use in this manner (lower and shorter doses) is certainly worth a second look.

Comments

  1. #1 Mountain Man
    January 15, 2008

    However, the new study RPM describes suggests this may be doing more harm than good ..

    Gee, there’s a novel thought — drugs worse than the disease.

    Where have I heard that one before?

  2. #2 Texas Reader
    January 16, 2008

    I think part of this issue is uncertainty regarding how long is ideal for taking certain drugs. I was in the hospital with pneumonia for 8 days. (I was so nauseated I couldn’t keep solid food down and they kept me until I was able to eat and thus go home and take the antibiotic doses that were via i.v. in the hospital by mouth.) My nurse told me a normal course of Levaquin was 10 daily doses. I had 8 in the hospital and they sent me home with a scrip for 4 more. Evidently the days of Levaquin for pneumonia is not established in a hard and fast manner. I took two of the four pills (which cost $25 each !) and then stopped due to gastro distress.

  3. #3 Left_Wing_Fox
    January 16, 2008

    Where have I heard that one before?

    The difference being that it’s heard one place as a blanket statement with non-specific terms of toxicology and cloaked in paranoia and conspiracy.

    In the other it’s linking specific effects with specific results by identifying the pathways and mechanisms in ways that can be reproduced to confirm or disprove the specific notion.

  4. #4 alan parker
    January 25, 2008

    Because of the risks associated with routine antibiotic use on farms, the Swedish government banned the use of antibiotics as growth promoters in 1986. With some improvements in hygiene and changes in diet, however, Swedish farmers were able to continue raising pigs almost as cheaply as before the ban. Other practices that reduce the need for antibiotics are vaccination and probiotics, the practice of using certain commensal bacteria to crowd out potential pathogens in an animal’s digestive system.