Enhanced delivery of antibiotics using outer membrane vesicles

Abstract Antibiotic resistance poses an immense global threat to human health, contributing to more than 2.8 million antimicrobial-resistant infections annually in the United States alone. This accounts for over 35,000 annual fatalities and an economic burden exceeding $4.6 billion for treatment. A formidable challenge in combating this issue lies in the intrinsic resistance of bacterial membranes, which restricts antibiotic uptake, thus diminishing their effectiveness. To overcome this challenge, we were inspired by outer membrane vesicles, naturally secreted by gram-negative bacteria, facilitating long-distance delivery of numerous biomolecules to the cytosol of target bacteria. We hypothesize that encapsulating antibiotics in outer membrane vesicles will provide stability and increased delivery to pathogens, resulting in more effective eradication. In this study, we used outer membrane vesicles produced by Escherichia coli JC8031 to augment the delivery of moxifloxacin to a range of both gram-positive and gram-negative pathogens. These included E. coli, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Streptococcus mutans, and Staphylococcus aureus, including clinical isolates exhibiting moxifloxacin resistance. Our findings revealed that antibiotic-loaded outer membrane vesicles exhibited comparable efficacy to free antibiotics in treating gram-negative pathogens and demonstrated superior efficiency in killing gram-positive pathogens. Specifically, when faced with clinical isolates of P. aeruginosa and S. aureus resistant to moxifloxacin, the antibiotics encapsulated in the outer membrane vesicles were much more effective. As we advance our research, future investigations will focus on identifying alternative antibiotics that display more effectiveness against gram-negative bacteria when encapsulated by outer membrane vesicles.