Restricting the use of antibiotics may not be enough to curb the spread of resistant bacteria, suggests new research in mice. Efforts will also have to focus on preventing infections by the superbugs in the first place.
These were the conclusions that scientists at ETH Zurich in Switzerland came to after identifying a previously unknown mechanism of antibiotic resistance spread in bacteria that inhabit the gut.
A recent Nature paper describes how, using mice, the team discovered the mechanism in persisters — persistent bacteria that can survive treatment with antibiotics by going into a dormant state.
“If you want to control the spread of resistance genes,” says co-senior study author Médéric Diard, “you have to start with the resistant microorganisms themselves and prevent these from spreading through, say, more effective hygiene measures or vaccinations.”
Until recently, Diard was working at ETH Zurich. He is now a professor at the University of Basel, also in Switzerland.
According to the World Health Organization (WHO), antibiotic resistance is a public health concern in every country.
In the United States, at least 2 million people develop antibiotic resistant infections each year, and at least 23,000 die from them, according to the Centers for Disease Control and Prevention (CDC).
Another mechanism of resistance spread
However, the findings of the new study suggest that restricting the use of antibiotics may not be enough to fight resistance because, thanks to persisters, it can spread without antibiotic use.
Persisters are bacteria that can wind down their metabolism to such an extent that they are barely still alive.
Scientists have known for some time that persisters exist and that antibiotics cannot kill these bacteria when they are in their dormant state.
Salmonella is a bacterium that can become a persister when it invades body tissues from the intestines.
This bacterium can lie dormant and escape detection for many months. When conditions become favorable, the germ can wake up and trigger infection.
However, even if the microbe does not cause infection to flare up, it can still pose a threat, according to the new findings.
Prof. Diard and his colleagues found that Salmonella has the ability not only to persist but also to carry resistance genes in the form of small pieces of DNA called plasmids.
In experiments in mice, the team showed that when the plasmid-carrying Salmonella persisters emerge from dormancy, they can readily share their resistance genes.
