In vitro activity of lysostaphin, mupirocin, and tea tree oil against clinical methicillin-resistant Staphylococcus aureus

Colonization of methicillin-resistant Staphylococcus aureus (MRSA) commonly leads to infection by the same strain. We examined the activity of lysostaphin, mupirocin, and tea tree oil against clinical MRSA (n = 98) isolates. MIC50 (range) were as follows: lysostaphin, 0.125 mg/L (0.125–0.25); mupirocin, 0.5 mg/L (0.19–1024); tea tree oil, 1024 mg/L (512–2048). High- and low-level mupirocin resistance was noted in 9.2% of our MRSA isolates. Time kill results indicate MRSA activity at 24 h was lysostaphin = gentamicin = vancomycin (P ≤ .001) > mupirocin > tea tree oil (P ≥ .05). Checkerboard testing indicated a synergistic relationship between lysostaphin and mupirocin in combination with gentamicin. Antagonism was observed with the combination of vancomycin and tea tree oil; time kill studies confirmed this result. Decolonization options are limited and resistance to mupirocin exists. Lysostaphin and tea tree oil may offer additional therapeutic options for the decolonization of MRSA where current treatment alternatives are limited.