The MRSA pathogen did not show any adaptation to the 3-drug treatment during lab tests with mice. Photo by BioMedical/Shutterstock

ST. LOUIS, Sept. 14 (UPI) -- A combination of 3 antibiotics was found in a study to kill methicillin-resistant Staphylococcus aureus, or MRSA, in all mice that were treated with it.

The research team has been working with antibiotics that are ineffective against specific pathogens that have evolved to resist them. The three drugs they tested against MRSA -- meropenem, piperacillin and tazobactam -- are members of a group of antibiotic called beta-lactams that have not had an effect against MRSA in decades.


When combined, the researchers reported it was as effective as one of the strongest drugs available to treat the pathogen.

"This three-drug combination appears to prevent MRSA from becoming resistant to it," said Dr. Gautam Dantas, an associate professor of pathology and immunology, in a press release. "We know all bacteria eventually develop resistance to antibiotics, but this trio buys us some time, potentially a significant amount of time."

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Researchers started off by testing out the drug combination on 73 different strains of the MRSA microbe, finding it was effective against all of them. When they began testing the combination on mice infected with MRSA, they found it cured the infection in every mouse. There was also no indication the pathogen was developing resistance to the combination during treatment.

In addition to testing out the effects of additional antibiotics that have become ineffective over time, based on the hope that combining them will make them useful again.

The researchers hope to try out the MRSA treatment out in humans.

"MRSA infections kill 11,000 people each year in the United States, and the pathogen is considered one of the world's worst drug-resistant microbes," said principal investigator Gautam Dantas, PhD, an associate professor of pathology and immunology. "Using the drug combination to treat people has the potential to begin quickly because all three antibiotics are approved by the FDA."

The study is published in Nature: Chemical Biology.