A study funded by the National Institutes of Health has found that a triple combination of antibiotics was effective in clearing methicillin-resistant Staphylococcus aureus (MRSA) infection in a mouse model (Gonzales PR et al. Nat Chem Biol. doi:10.1038/nchembio.1911 [published online September 14, 2015]).
Researchers at the Washington University School of Medicine in St Louis and University of Notre Dame found that the triple combination of β-lactam antibiotics meropenem, piperacillin, and tazobactam, which work synergistically to disrupt bacterial cell wall synthesis, was more effective in vitro against a strain of MRSA resistant to 23 different antibiotics than any of the 3 antibiotics used alone or in pairs. This triple-antibiotic combination was also effective in vitro against other MRSA strains obtained from 72 clinical MRSA cases. Furthermore, when the MRSA bacteria were exposed to low doses of the triple-antibiotic combination for 11 days in culture, resistance to the drugs did not develop, whereas resistance developed within 1 to 8 days when the antibiotics were used alone or in pairs.
Jacob JA. Triple Combination of Antibiotics Effective Against MRSA. JAMA. 2015;314(20):2121. doi:10.1001/jama.2015.15801