Antibacterial and Anti-Biofilm Effect of Silver Nanoparticles Synthesized from Origanum majorana and Echinacea purpurea (L.) Moench Plants via Green Synthesis

Objective: Nanotechnology has gained importance in the fight against epidemics and antibiotic resistance. Nanotechnology is a potential way to prevent the increase of multidrug-resistant bacterial species. The aim of this study was to determine the antimicrobial and anti-biofilm activities of Origanum majorana and Echinacea purpurea silver nanoparticles (AgNPs) against Staphylococcus aureus (S.aureus) ATCC 25923, Escherichia coli (E.coli) 25922, Pseudomonas aureginosa (P.aureginosa) 27853, Klebsiella pneumoniae (K. pneumoniae) 700603. Methods: Minimum Inhibitory Concentration (MIC) values of silver nanoparticles were determined by microdilution method in 96-well ELISA plates. The anti-biofilm effect of silver nanoparticles was performed by crystal violet method in 96-well microplates. Results: The MIC value of four isolates was determined as 128 µg/ml for two nanoparticles. Only 256 µg/ml and 512 µg/ml were found for S. aureus. In vitro, anti-biofilm effect of AgNPs against biofilm forming bacteria was evaluated in a dose-dependent manner. S. aureus, AgNP synthesized from Origanum majorana plant extract (512 µg/ml) reduced biofilm formation by 92% after 24 hours of incubation. As a result of 24 hours incubation of S. aureus with AgNP (512 µg/ml) synthesized from Echinacea purpurea (L.) It was determined that biofilm formation decreased by 85%. It was observed that both different nanoparticles significantly inhibited the biofilm mass. Conclusion: AgNPs showed antimicrobial and antibiofilm effects for standard strains. The use of AgNPs as antimicrobials is promising for the future.