Scientists may have discovered a weakness in a strain of multidrug-resistant bacteria that turns off antibiotic resistance when attacking other bacteria. The research is described in The Proceedings of the National Academy of Sciences.

The team from Washington University School of Medicine in St. Louis, MO reviewed samples of Acinetobacter baumannii from a 2012 outbreak in a Canadian hospital. In order to kill off other bacteria, the multidrug-resistant A. baumannii produce and inject a poison into their bacterial competitors. However, in these samples the A. baumannii’s poison injection system was shut down due to sections of bacterial DNA known as plasmids. The plasmids also carried genes than enabled the bacteria to resist antibiotics. The scientists found that part of the bacterial population regularly deactivated the plasmids, which turned on the poison injection system and transformed the bacteria into killers. But doing so meant the bacteria also turned off the antibiotic-resistance genes, making the bacteria vulnerable to antibiotics. This indicates that there was a trade-off for the bacteria, as the bacteria’s ability to kill competitors left them vulnerable to antibiotics when the poison injection system was activated.

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If other strains of bacteria could be forced to undergo this change, it could help reduce the spread of multidrug-resistant strains and lead to more effective treatments and strategies for preventing the spread of infectious diseases.

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