Vancomycin-Loaded Isogenous Membrane Vesicles for Macrophage Activation and Intracellular Methicillin-Resistant Staphylococcus aureus Elimination.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA), a notorious multidrug-resistant (MDR) pathogen, frequently resides and proliferates within macrophages, contributing to refractory and recurrent infections. Conventional antibiotics exhibit limited efficacy against intracellular MRSA due to poor cellular penetration. METHODS: Vancomycin (VAN) was encapsulated into membrane vesicles ((ΔagrA)MVs) derived from the attenuated S. aureus strain RN4220ΔagrA, generating VAN-loaded nanoparticles ((ΔagrA)MV-VAN). In vitro and in vivo experiments were performed to test the efficacy of (ΔagrA)MV-VAN in intracellular MRSA clearance. RESULTS: (ΔagrA)MV-VAN demonstrated sustained VAN release and efficient extracellular MRSA eradication. Moreover, macrophages actively internalized (ΔagrA)MV-VAN, leading to VAN accumulation in intracellular compartments and M1 macrophage polarization, which increased MRSA killing. In vivo animal experiments revealed that (ΔagrA)MV-VAN was safe and effectively eliminated intracellular MRSA in abdominal infections. CONCLUSION: Our findings propose a nanotherapeutic strategy that uses bacterial-derived vesicles for targeted antibiotic delivery, overcoming the intrinsic limitations of conventional therapies against intracellular MDR pathogens.