Phytochemical-Mediated Synthesis of Silver Nanoparticles Using Apis mellifera (Honeybee) Propolis and Their Enhanced Antibacterial Efficacy Against Multidrug-Resistant Pathogens

The escalating crisis of antimicrobial resistance necessitates the urgent development of novel, effective, and biocompatible therapeutic agents. This study reports a sustainable, phytochemical-mediated approach for synthesizing silver nanoparticles (Pro-AgNPs) using the ethanolic extract of Apis mellifera (honeybee) propolis, a complex natural resin renowned for its broad-spectrum bioactivity. The bioactive compounds in propolis, primarily flavonoids and phenolic acids, served a dual function as reducing and capping agents, facilitating the eco-friendly synthesis of stable nanoparticles. Comprehensive characterization confirmed the successful formation of crystalline, spherical Pro-AgNPs with an average size of 22.4 ± 5.8 nm, as evidenced by UV-Vi’s spectroscopy (surface plasmon resonance at ~435 nm), X-ray diffraction (peaks corresponding to face-cantered cubic silver), and electron microscopy. Crucially, the synthesized Pro-AgNPs demonstrated significantly enhanced in vitro antibacterial efficacy against a panel of clinically relevant multidrug-resistant (MDR) pathogens—including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci, and extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae—when compared to pure propolis extract or silver nitrate solution. The determined minimum inhibitory concentrations (MICs) for Pro-AgNPs were substantially lower (8–32 µg/mL), highlighting a potent synergistic effect. The enhanced activity is attributed to a concerted "hybrid nano-bio" mechanism, where propolis phytochemicals compromise bacterial membrane integrity and inhibit efflux pumps, thereby potentiating the multifaceted antimicrobial action of the silver nanoparticles, which include membrane disruption, reactive oxygen species generation, and intracellular damage. These findings underscore propolis as an exceptional natural precursor for green nanotechnology and position Pro-AgNPs as a promising, synergistic nano-antibacterial platform with significant potential for combating multidrug-resistant infections.