Bacteria that survive an antibiotic attack emerge stronger, with an ability to repel new drugs – but why?
The conventional idea is that susceptible bugs perish, leaving behind a few individuals whose drug resistance is passed on as they multiply. This does not, however, explain why bacteria treated with one drug tend to resist others too.
Now Jim Collins at Boston University and his team have found that several different kinds of antibiotics can actively create mutations that confer this multidrug resistance.
The antibiotics produce toxic molecules called free radicals that damage the DNA of Escherichia coli, and the resulting mutations are locked in when a sloppy repair system fails to put the DNA back together properly. "What doesn't kill them makes them stronger," says Collins. He hopes that blocking DNA repair will slow the emergence of multidrug-resistant superbugs .
Morten Sommer a microbiologist Harvard Medical School in Boston, calls the discovery "very important". Levels of antibiotics vary throughout the body during treatment, but they are most likely to create new mutations where drug levels are low.
Journal reference: Molecular Cell, DOI: 10.1016/j.molcel.2010.01.003
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