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Tuesday, December 02, 2003 Are We Responsible For Creating Superbugs? In a recent Science paper ("A Bacterium's Borrowed Weapon" is a simplified summary), a collaboration at the CDC and the University of Michigan determined the probable mechanism through which Staphylococcus aureus acquired vancomycin resistance. Vancomycin, if you're not familiar with it, is one of those drugs you use as the last resort and if the infection is resistant to it--well, to say the least, you're in big trouble. So far, though, the vancomycin-resistant strain of S. aureus (or VRSA) has only been isolated in Michigan so the general public doesn't feel like it has to worry. Yet. But that's the problem. Most people don't feel the need to work on interesting and potentially dangerous problems unless it has affected most of the population or some famous person with a lot of clout. So how do microbes, specifically bacteria, become resistant to all these drugs? I think the answer to that question is quite simple--they become resistant because we select for them. Let's say a patient has a bacterial infection. In this person, there is a population of bacteria that is growing uncontrollably. The person's immune system may or may not be able to contain it in time. The doctor then gives the patient a drug. If the drug kills 99.999% of the bacteria, the 0.001% that remains alive because they are resistant could expand again--but this time giving rise to an infection that cannot be eliminated through the original drug. The same thing will happen to whatever else we throw at the bug. Well, why don't we just develop or find new drugs or modify old drugs? First of all, there are only so many targets that a drug can hit: cell wall synthesis, DNA replication, RNA synthesis, antimetabolites, protein synthesis. There is also the problem of selective toxicity. Drug X may kill the bacteria, but it may also kill mammalian cells as a lot of cellular machinery has been conserved throughout evolution. The thing is--if we come up with something to solve the problem, nature probably has already figured out a way around it. And even if a drug can be found to target one particular bacteria, it wouldn't be a very practical drug in the viewpoint of a practicing physician. Doctors are afraid to be wrong and would rather throw a drug that can act on a wide variety of diseases rather than one specific one--because if the disease isn't that one specific one, the life of the patient may be in serious jeopardy. There is currently no definitive solution for this problem. And one must admit, the problem is actually being exacerbated rather than relieved by the elaborate cocktails of drugs being produced for immunodeficient diseases such as HIV. So what can we do? We can start screening through libraries of chemical compounds, for one. But I personally don't think we'll be able to outwit nature unless we think of a completely different way of approaching the problem besides just going one by one through different compounds that a bacterium will certainly get over. [posted by S. Y. Affolee on 5:44 PM : ]
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