Combination of Three Antibiotics Effective Against MRSA Bacteria

Researchers at the Washington University School of Medicine in St. Louis, have found that a combination of three antibiotics is an effective treatment against Methicillin-resistant Staphylococcus aureus (MRSA) infection. When used individually these antibiotics are ineffective at killing MRSA bacteria, but when used in conjunction with one another, new research suggests they may be a valuable tool.

The researchers combined three antibiotics – meropenem, piperacillin and tazobactam – and tested their efficacy against MRSA both in vitro and in vivo. Though the in vivo studies were performed in mice, the researchers are hopeful that the same combination of antibiotics may be effective in human patients.

“MRSA infections kill 11,000 people each year in the US, and the pathogen is considered one of the world’s worst drug-resistant microbes,” said Gautam Dantas, a Washington University pathology and immunology associate professor and principal investigator, and the study’s principal investigator. “Using the drug combination to treat people has the potential to begin quickly because all three antibiotics are approved by the FDA.”

These three drugs belong to a class of antibiotics known as beta-lactams. Though these antibiotics used to be useful at fighting infections, they have been ineffective against MRSA bacteria for decades.

In collaboration with researchers from the microbiology laboratory at Barnes-Jewish Hospital, Dantas and his team studied 73 strains of MRSA bacteria, in an effort to understand the genetics of both community and hospital-acquired forms of the infection. The triple antibiotic treatment was tested against many of these strains, and it was found to be effective at killing every variant tested.

“Without treatment, these MRSA-infected mice tend to live less than a day, but the three-drug combination cured the mice,” said Dantas. “After the treatment, the mice were thriving.”

The drugs were found to act in a synergistic manner, to attack and break-down the bacterial cell wall. Importantly, the three-drug treatment did not induce further antibacterial resistance in the MRSA pathogen – a common concern as more and more available antibiotics are becoming ineffective due to increased resistance.

“This three-drug combination appears to prevent MRSA from becoming resistant to it,” said Dantas. “We know all bacteria eventually develop resistance to antibiotics, but this trio buys us some time, potentially a significant amount of time.”

Dantas and his team are also testing other previously-ineffective drugs to see if they would work against resistant bacteria, if used in conjunction with other antibiotics. Dantas said, “We started with MRSA because it’s such a difficult bug to treat. But we are optimistic the same type of approach may work against other deadly pathogens, such as Pseudomonas and certain virulent forms of E coli.”

Sources:

• US researchers find combo of three antibiotic drugs kills staph infections – http://www.pharmaceutical-technology.com/news/newsus-researchers-find-combo-three-antibiotic-drugs-kills-staph-infections-4672282