New method may spell end for superbugs

Researchers have identified a new method to restore drug-resistant bacteria's vulnerability to antibiotics, an advance that may lead to better strategies to prevent the development of deadly superbugs.
Infections with one of the most troublesome and least understood antibiotic-resistant superbugs are increasing, particularly in health-care settings, researchers said.
However, the researchers at Washington University School of Medicine suggest it may be possible to rein in the spread of such infections without developing new antibiotics.
Bacteria are natural competitors and have the capacity to kill off other bacteria.
However, to become bacterial assassins, the researchers found that multidrug-resistant Acinetobacter baumannii, a frequent cause of difficult to treat infections in hospitals, has to relinquish its ability to defy antibiotics.

"If we can identify ways to force the entire population of drug-resistant bacteria to undergo this change, we stand a better chance of fighting the growing problem of antibiotic resistance," said first author Brent Weber, a graduate student at Washington University.

"Instead of looking for new antibiotics, we could restore bacteria's vulnerability to antibiotics we already have," Weber said.
The researchers studied samples of A baumannii isolated from a 2012 outbreak at a Canadian hospital.
"Many strains of this type of bacteria are resistant to antibiotics, can survive disinfectants and rapidly are becoming major health problems in hospitals worldwide," said senior author Mario Feldman of Washington University.

The researchers expected the A baumannii to readily kill other bacteria by injecting a poison into their bacterial competitors, for the infections to spread widely and quickly.
Instead, the scientists found that the bacteria's poison injection system was disabled in most of the samples from the Canadian outbreak.
They identified chunks of bacterial DNA that were shutting down the system. These pieces of DNA, known as plasmids, also carried genes that enabled the bacteria to resist antibiotics.
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.

However, this meant the bacteria also turned off the antibiotic-resistance genes, making it vulnerable to antibiotics.
Studies of A baumannii samples from other outbreaks worldwide found the same trade-off - the bacteria's ability to kill competitors left them unable to resist antibiotics.
"This knowledge could lead to more effective treatments and better strategies for preventing the development of superbugs," Feldman said.
The study was published in the journal PNAS.