Mostly dead bacteria can sometimes be resurrected as antibiotic-resistant cells.
A protein that pumps toxic chemicals out of E. coli bacterial cells can buy time for even nearly dead microbes to become antibiotic resistant. The protein, known as the AcrAB-TolC multidrug efflux pump, doesn’t work well enough to defeat antibiotics on its own. But it can move enough antibiotic molecules out of bacterial cells to allow production of real resistance proteins, researchers report in the May 24 Science.
Bacteria often swap DNA, including some antibiotic-resistance genes. Scientists have known for decades that antibiotic-resistance genes are often carried on small circles of DNA called plasmids. Two bacteria that come in contact with each other can pass these plasmids from antibiotic-resistant cells to sensitive ones. But that was thought to happen when antibiotics aren’t around to kill sensitive cells.
Common wisdom holds that treating bacteria with antibiotics should stop bacteria in the act of swapping antibiotic-resistance genes, says Kim Lewis, a microbiologist at Northeastern University in Boston not involved in the study. At least, “yesterday, that’s what I would have told you,” he says. “Today, having read that paper, I have to change my views.”