Resistance makes use of sleeping bacteria

Salmonellae (image from an electron microscope)

Bacteria can evade antibiotics by going into a kind of deep sleep, then pass on resistance genes even if they are not resistant themselves.

Salmonellae (image from an electron microscope) (Photo: ETH Zurich / Stefan Fattinger)

Besides building up resistance, bacteria can also protect themselves against antibiotics by lapsing into a passive state and waiting for the effect of the antibiotics to wear off. Importantly, these so-called persisters are not only responsible for recurring infections, they also serve as a reservoir for the transmission of resistance, as researchers from ETH Zurich discovered in an NRP 72 project.

Their results, which have been published in the journal Nature, show that persisters in salmonellae often carry a small DNA fragment (plasmid) containing resistance genes. When the bacteria awake from their period of inactivity, they are able to pass on their resistance genes - both within their own species and to other bacteria, such as the coli bacteria found in normal intestinal flora. The genes are transmitted irrespective of whether any antibiotics were used. These findings suggest that, besides using less antibiotics, it is also important to prevent resistant germs from spreading.