A new approach to targeting S. aureus

Antibiotic-resistant strains of Staphylococcus aureus, such as methicillin-resistant S. aureus (MRSA), are proving increasingly difficult to treat. This study confirms that one reason for this is the ability of the pathogen to reside in intracellular reservoirs where they are protected from antibiotics. To counter this barrier, the authors develop a new strategy — based on an antibody–antibiotic conjugate (AAC) — to specifically target these reservoirs. The antibody binds to wall teichoic acids on the surface of S. aureus cells, and internalization of AAC-opsonized bacteria by host cells results in removal by host proteases of the linker between the antibody and the antibiotic, thereby releasing the antibiotic in its active form. A single dose of AAC is effective in a mouse model of bacteraemia, and is superior to the use of vancomycin, the current standard of care for MRSA infection. These findings are a proof-of-principle for the possibility of using antibody carriers to deliver existing antibiotics in a way that could ensure their continued clinical success.