One-pot biosynthesis of silver nanoparticles with potential antimicrobial and antibiofilm efficiency against otitis media-causing pathogens

There are increasing demands for biogenic synthesis of silver nanoparticles (AgNPs) due to their unique properties and their numerous applications especially in biomedical field. Direct sunlight irradiation on aqueous garlic extract (AGE) represent fast, applicable, non-toxic, cheap, and ecofriendly method for (AgNPs) synthesis, with potentials to compete multi-drug-resistant (MDR) and biofilm-forming pathogens causing otitis media (OM). The aim of this study was to establish an eco-friendly method for synthesis of AgNPs, using aqueous garlic extract and sunlight, and moreover, detect its potential to inhibit MDR OM microbes. Obtained AgNPs were characterized by UV-visible spectral analysis, TEM, DLS, XRD, and FTIR. The effect of biosynthesized AgNPs on microbial growth, as well as biofilm productivity, was assessed against five resistant OM-causing strains, namely Bacillus cereus, Pseudomonas aeruginosa, Penicillium chrysogenum, Aspergillus niger, and Aspergillus flavus. Kirby-Bauer disc diffusion method was used to assess the inhibitory effect of 100, 50, 25, 12.5, and 6.25 μg/ml of AgNPs compared with tetracycline or nystatin and AGE. Additionally, the effect of 25 μg/ml of AgNPs on biofilm productivity of such strains was qualitatively assessed using Congo red agar (CRA) and TEM used to capture the changes inside the selected strains. The obtained AgNPs showed a highly significant (p value < 0.001) antimicrobial and antibiofilm activities against tested strains. TEM images of Pseudomonas aeruginosa and Aspergillus flavus treated with 25 μg/ml AgNPs showed shrinkage in the cytoplasmic materials and rupture of cell walls.

Keywords: Aqueous garlic extract; Bacillus cereus; Penicillium. Aspergillus; Pseudomonas aeruginosa; Sunlight irradiation.