Oops! Maybe you don’t need to take that full course of antibiotics after all

You know how the doctor tells you to take all the antibiotic pills he/she prescribes? That advice may be all wrong. Supposedly the point of taking the full course of pills is to kill off any bugs that may have developed resistance to the antibiotic. That is, you’ll be sure to kill off the tougher bugs if you take all the pills in the bottle.

That doesn’t make sense. Why would some of the bugs develop resistance if you stop taking your antibiotics? A biological engineer from MIT says “The risk you run,” he said, is that “the longer you use antibiotics, you increase your risk of developing resistance.” More bugs have more opportunities to develop resistance and those bugs proliferate.  

Current experiments on streptococcus have shown that the susceptible bugs were killed by antibiotics within three days of taking the drug. But the bugs that were resistant to the antibiotic were still hanging around in low numbers six months after the initial treatment. In Darwinian terms, this amounts to survival of the fittest.

It turns out that the medical community doesn’t really know the optimal dose required to kill off various pathogens. (Exceptions: if you have tuberculosis or a staph blood infection, take all the pills.) As one researcher says, the idea of taking a full course of antibiotics “has come down from our forefathers and is not based on modern scientific evidence.”

Apparently, not much research has been done to determine the optimal dosing for killing bad bugs and at the same time avoiding the development of resistance. Some scientists are now trying to figure this out. But it’s very tricky business. As another researcher says, “It’s a very complex relationship between antibiotic use and resistance, and every antibiotic has selection potential” (that is, the potential to encourage the growth of resistant bugs). To get it right, they have to do experiments with each bad bug to get the right antibiotic and right dose.

Sounds like right now it’s a bit of a crap shoot.

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