Targeting Resistant Staphylococcus aureus with small Extracellular Vesicles from Human Adipose-Derived Stromal Vascular Fraction
- Department of Microbiology, Central Research Laboratory and Nitte University Centre for Stem Cell Research & Regenerative Medicine (NUCSReM), KS Hegde Medical Academy (KSHEMA), Nitte (Deemed to be University), Deralakatte, Mangaluru 575018, India
- Department of Plastic Surgery, KS Hegde Medical Academy (KSHEMA), Nitte(Deemed to be University), Deralakatte, Mangaluru 575018, India
- Nitte University Centre for Stem Cell Research & Regenerative Medicine (NUCSReM), KS Hegde Medical Academy (KSHEMA), Nitte (Deemed to be University), Deralakatte, Mangaluru 575018, India
- Central Research Laboratory, KS Hegde Medical Academy (KSHEMA), Nitte (Deemed to be University), Deralakatte, Mangaluru 575018, India
Abstract
Introduction: Antimicrobial resistance (AMR), particularly involving antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), poses a critical global health challenge. Driven primarily by the mecA gene, MRSA is prevalent in both healthcare and community settings and continues to cause severe infections and high mortality worldwide, despite the availability of antibiotics. The COVID-19 pandemic further highlighted the limitations and adverse effects of conventional synthetic antibiotics and cell-based therapies, emphasizing the urgent need for safer, innovative, and preferably natural, cell- and drug-free therapeutic approaches.
Objective: Given the well-established immunomodulatory properties of human adipose tissue, adipose-derived vesicles were selected as a biologically relevant, economical, non-invasive, and promising therapeutic candidate for this investigation. This study investigated the intrinsic antibacterial and antibiofilm properties of small extracellular vesicles (sEVs) derived from the stromal vascular fraction (SVF) of healthy human adipose tissue (hHAT) against MRSA, thereby addressing a critical research gap in current AMR treatment strategies.
Methods: SVF‑sEVs from hHAT were isolated using the established Priglinger method and characterized in accordance with MISEV 2023 guidelines. Their antibacterial activity was evaluated in vitro against both MRSA and methicillin-sensitive S. aureus (MSSA) strains—comprising American Type Culture Collection (ATCC) reference strains and clinical isolates (CS)—across multiple time points. Plain phosphate-buffered saline (PBS), devoid of antibiotics or antifungals, served as the negative control. Following the confirmation of antibacterial efficacy, the concentration-dependent inhibition of biofilm formation was assessed for MRSA, MSSA, and the rpoA reference strain, given the pivotal role of biofilms in AMR.
Results: Naturally occurring, cell-free, nanoscale neat SVF-sEVs (EVN; 100 µL, containing 2.15 × 10⁹ sEVs/100 µL) exhibited antibacterial activity against both MRSA and MSSA, alongside a concentration-dependent inhibition of biofilm formation, including in the rpoA reference strain. These effects were confirmed quantitatively via colony-forming unit (CFU) counts and qualitatively via zone of inhibition (ZOI) assays, revealing a significant modulation of bacterial viability and biofilm development. The ATCC MSSA strain demonstrated the largest inhibition zones, the CS-MRSA strain exhibited the greatest reduction in colony counts, and the ATCC MRSA strain showed significant antibiofilm effects.
Conclusions: SVF‑sEVs constitute a novel, biocompatible, and ethically sound therapeutic strategy against MRSA. They offer a promising adjunct or alternative to conventional antibiotics, with a potentially lower risk of driving antimicrobial resistance.