Purpose: The aim was to evaluate the antimicrobial potential of AgNPs synthesized with Artemisia argyi  leaf extract and investigate the antimicrobial synergistic effects of AgNPs combined with domiphen and provide an efficient and broad-spectrum combination drug strategy.
Methods: AgNPs synthesized with Artemisia argyi  leaf extract were studied using UV–vis spectroscopy, FTIR spectroscopy and particle size analysis. Then, Artemisia argyi  leaf extract-synthesized AgNPs and domiphen were tested against Acinetobacter baumannii  (ATCC 19606), Staphylococcus aureus  (ATCC 6538), Escherichia coli  (8099) and Candida albicans  (ATCC 10231), respectively. Then, we explore synergistic antimicrobial effect and synergistic anti-biofilm effect through combined drug susceptibility test and combined drug minimum biofilm eradication concentration (MBEC₅₀) test.
Results: Characteristic absorption bands of AgNPs were found near 430 nm in the UV–vis spectrum. Particle size analysis results revealed that the average particle size of Artemisia argyi  leaf extract-synthesized AgNPs was 77.6 nm. Artemisia argyi  leaf extract-synthesized AgNPs showed high antimicrobial activity against the above four strains. Minimum inhibitory concentration (MIC) of Artemisia argyi  leaf extract-synthesized AgNPs against strains was 1 μg/mL for Acinetobacter baumannii , 2 μg/mL for Staphylococcus aureus, Escherichia coli  and Candida albicans . MBEC₅₀ of Artemisia argyi  leaf extract-synthesized AgNPs against strains was 2 μg/mL for Acinetobacter baumannii , 4 μg/mL for Staphylococcus aureus , 1/2 μg/mL for Escherichia coli  and 2 μg/mL for Candida albicans . The combination of Artemisia argyi  leaf extract-synthesized AgNPs and domiphen has synergistic antimicrobial effect and synergistic anti-biofilm effect. Fractional inhibitory concentration (FIC) was ≤ 0.5.
Conclusion: Artemisia argyi  leaf extract-synthesized AgNPs had antimicrobial activity against the above four strains. The combination of Artemisia argyi  leaf extract-synthesized AgNPs and domiphen has synergistic antimicrobial effects to reduce the dosage of each antimicrobial drugs. Artemisia argyi  leaf extract-synthesized AgNPs and domiphen have synergistic anti-biofilm effects.
Keywords: AgNPs, domiphen, synergy, pathogenic biofilm, combination medication