How Resistance Arises

The ability of infectious bacteria to quickly evolve resistance to antibiotic drugs is a major problem. Some strains can withstand every antibiotic we have, and we’re struggling to come up with new versions. One reason is that we don’t fully understand how bugs make themselves impervious. But now researchers are revealing some of the steps involved. When Escherichia coli is exposed to the antibiotic ciprofloxacin, it changes its usual rod shape into elongated filaments (pictured), each containing multiple chromosomes. Here, mutations are induced that eventually produce mutant chromosomes with resistance to ciproflaxacin. Finally, the filament divides repeatedly at the tip, giving rise to antibiotic-resistant offspring cells. It’s not clear how the cells know when to stop shuffling DNA and start dividing. But it seems that the generation of multiple mutant chromosomes in the filaments is vital in the development of antibiotic resistance.

Written by Daniel Cossins

Daniel Cossins

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As a freelance science writer, Dan's work has been published in award-winning magazines including BBC Focus, Wired UK, Cosmos, BBC Knowledge, BBC History and Men's Health.

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• Image by Robert H. Austin and colleagues
• Princeton University, USA
• Image copyright held by original authors; image reproduction permitted by PNAS
• Research published in PNAS, January 2015