Bacterial Resistance to Antibiotics

The prevailing thought has always been that bacterial resistance to antibiotics comes about by a process of natural selection. When antibiotics kill most but not all of a bacterial population, the bacteria that survive are those that were most resistant to the antibiotic. These resistant bacteria then flourish, passing their resistance genes on to other bacteria and outcompeting their more vulnerable kin. The more times an antibiotic is used, then, the more likely it becomes that the surviving bacteria will be resistant to it.

But now researchers have found another mechanism for bacterial resistance to antibiotics. It turns out that antibiotics induce the formation of toxic molecules within bacteria called reactive oxygen species, or free radicals, that help kill the bacteria. But if the concentration of antibiotic is below the threshold for killing the bacteria outright, the free radicals cause mutations in the bacteria, some of which by random chance may confer drug resistance. In other words, antibiotics speed up the process of bacterial evolution in the surviving bacteria.

The finding opens a new avenue for research – finding molecules that prevent this bacterial mutagenesis, thus perhaps delaying the development of antibiotic resistance.