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Salk Scientists Fight Harmful Bacteria With More Bacteria

In a study published in Science on Thursday, scientists at the Salk Institute show that mice infected with harmful bacteria can get a boost from helpful bacteria.

In a study published in Science on Thursday, scientists at the Salk Institute show that mice infected with harmful bacteria can get a boost from helpful bacteria.

The mice were battling salmonella and pneumonia, which can both take a physical toll on the body by causing muscle-wasting. Antibiotics are a standard part of treatment for these bacterial infections, but overusing them can lead bacteria to evolve drug-resistance.

"We're running out of our antibiotics of last-resort," said Salk assistant Janelle Ayres, who's searching for new ways of treating infectious disease that move beyond antibiotics.

Through a series of experiments, Ayres and her colleagues identified a strain of E. coli that helped stave off muscle-wasting in infected mice. A dose of this beneficial bacteria didn't kill off harmful bacteria, but it did lessen its physical toll.

"We figured out that we could directly administer this E. coli to the wasting-susceptible animals, and we could basically rescue their muscle-wasting," Ayres said.

Ayres said the bacteria helped mice by activating a component of the immune system that promotes a growth-stimulating hormone. More research is needed to determine whether a similarly helpful bacteria exists in humans.

UC San Diego's Rob Knight, who was not involved in the study, commented on the research in an email, writing, "These results add to the growing evidence in mice that your microbiome alters whether specific pathogens can infect you — if you’re a mouse. In humans, it will take longer to figure out."

Knight directs UC San Diego's new Center for Microbiome Innovation. The center was launched this week in part to accelerate research into the connections between human health and the trillions of microbes that inhabit our bodies.

Ayres said the next step for her research will be testing whether beneficial microbes could hold back physical damage in mice long enough for the body to get rid of a pathogen naturally.

"Now we're looking at whether we've bought the animals enough time for their own immune system to kick in and clear the infection," she said.

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