Friday, 13 March 2020

One quarter of bacterial pathogens spread antibiotic resistance directly

Biomedical engineers at Duke University have demonstrated that at least 25 percent of antibiotic-resistant pathogenic bacteria found in clinical settings are capable of spreading their resistance directly to other bacteria. At the same time, the study shows that, despite common beliefs, the use of antibiotics does not significantly affect the rate at which the genes responsible for resistance are swapped between bacteria.

Researchers used a new high-throughput method of measuring the rate at which bacteria exchange the packages of DNA that bestow resistance. The speed and ability to automate much of the process could allow new insights into what variables affect transfer rates. Such efforts could help doctors slow -- or even reverse -- the spread of resistance in certain human pathogens.

Each antibiotic-resistant pathogen carries a genetic recipe for its resistance. But like chocolate chip cookies, not all recipes are the same, and not all of them are easily taught to others. One way of transferring resistance, however, is for that genetic recipe to be neatly written into a sharable book of sorts called a plasmid, which is then picked up and read by a neighboring bacteria through a process called conjugation.

As resistance to antibiotics grows around the world, scientists are trying to figure out how to stop it from spreading. But because a lot of antibiotics come from natural sources, it would be impossible to completely eliminate resistance in the wild, which means there will always be reservoirs of bacteria filled with recipe books for resistance.

By measuring the rate of plasmid conjugation both with and without beta-lactamase antibiotics present, researchers showed that, except for one outlier, these antibiotics do not increase the rate of sharing resistance. They also discovered that more than 25 percent of the strains studied are capable of sharing their resistance at rates fast enough to detect.


Jonathan H. Bethke, Adam Davidovich, Li Cheng, Allison J. Lopatkin, Wenchen Song, Joshua T. Thaden, Vance G. Fowler, Minfeng Xiao, Lingchong You. Environmental and genetic determinants of plasmid mobility in pathogenic Escherichia coli. Science Advances, 2020; 6 (4): eaax3173 DOI: 10.1126/sciadv.aax3173

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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