Antibacterial synergy of Tritirachium oryzae-produced silver nanoparticles with different antibiotics and essential oils derived from Cupressus sempervirens and Asteriscus graveolens (Forssk)

摘要

Purpose: To carry out eco-friendly biosynthesis of fungi-derived silver nanoparticles (AgNPs) and investigate their antibacterial synergies with essential oils (EOs) of Asteriscus graveolens (Forssk.) Less. and Cupressus sempervirens. Methods: Biosynthesis of AgNPs was carried out using a cell-free filtrate of Tritirachium oryzae. The biosynthesized AgNPs characteristics were assessed using different methods, including ultraviolet-visible spectrophotometry (UV), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results: Obvious synergistic effects were observed between AgNPs and chloramphenicol, vancomycin, nitrofurantoin or tetracycline with Pseudomonas aeruginosa, through increases in fold area of inhibition (IFAs) within the range of 2.4 to 9.0. Synergistic interactions were also seen between AgNPs and the antibiotics used, depending on the strain. Increase in IFA ranged from 1- to 3-fold for S. aureus, E. coli and P. aeruginosa. Similarly, combinations of AgNPs, EO of A. graveolens and cefotaxime, nitrofurantoin or amoxicillin against P. aeruginosa led to 10-, 3- and 10-fold synergy, respectively. In contrast, the use of AgNPs and trimethoprim, tetracycline or amoxicillin against E. coli led to 1 to 6-fold synergy. The best synergistic capacity resulted from AgNPs and the EO of C. sempervirens and trimethoprim against S. epidermidis, which yielded 29-fold increase in IFA. The use of combination of AgNPs and vancomycin against P. aeruginosa led to 16.4-fold enhancement of IFA. Conclusion: The findings can potentially lead to the development of a new perception of antibacterial agents (innovative medications) involving the incorporation of nanoparticles (NPs) or new materials that potentially synergize with antibiotics, NPs and the EOs of different plants.