Recombinant Lysostaphin Protects Mice from Methicillin-Resistant Staphylococcus aureus Pneumonia

The advent of methicillin-resistant Staphylococcus aureus (MRSA) and the frequent and excessive abuse of ventilators have made MRSA pneumonia an inordinate threat to human health. Appropriate antibacterial therapies are crucial, including the use of lysostaphin as an alternative to antibiotics. To explore the potential use of lysostaphin as a therapeutic agent for MRSA pneumonia, mice were intranasally infected with MRSA and then treated with recombinant lysostaphin (rLys; 45mg/kg in the high-dose group and 1mg/kg in the low-dose group) (0.33mg/mL, 15mg/mL), vancomycin (120mg/kg) (40mg/mL), or phosphate-buffered saline (PBS, negative control) 4 h after infection. Therapeutic efficacy was assessed by mouse survival, lung histopathology, bacterial density in the lungs, bodyweight, lung weight, temperature, white blood cells counts, lymphocytes counts, granulocytes counts, and monocytes counts. The mice treated with rLys showed lower mortality, less lung parenchymal damage, and lower bacterial density at metastatic tissue sites than mice treated with PBS or vancomycin. The overall mortality was 100%, 60%, 40%, and 60% for the control, vancomycin, high-dose rLys, and low-dose rLys groups, respectively. These findings indicate that, as a therapeutic agent for MRSA pneumonia, lysostaphin exerts profound protective effects in mice against the morbidity and mortality associated with S. aureus pneumonia.