Antibacterial and synergistic effect of biosynthesized silver nanoparticles using the fungi Tritirachium oryzae W5H with essential oil of Centaurea damascena to enhance conventional antibiotics activity

Abstract The aims of this study are to synthesis silver nanoparticles (AgNPs) using the culture supernatant of the fungal strain Tritirachium oryzae W5H and to investigate the antibacterial activity of AgNPs individually and in combination with some antibiotics and essential oil of the plant Centaurea damascena. The colour of the filtrate with silver nitrate solution changed to intense brown after 72 h of incubation. The UV – Vis is spectrum shows a surface plasmon resonance (SPR) peak of AgNPs at 425 nm. For confirmation of the presence of AgNPs in the solution, analysis of transmission electron microscopy (TEM) image, scanning electron microscope (SEM) micrograph and SEM-EDS were recorded. The current study showed that AgNPs possess broad spectrum activity with inhibition zone ranged from 12 nm to 22 mm. Notable synergy was seen between AgNPs and either vancomycin, nitrofurantoin, chloramphenicol or tetracycline, against Pseudomonas aeruginosa , with a 2.4-fold to 9-fold, increase in fold area of inhibition (IFA). Similarly, AgNPs with gentamicin, tetracycline, ampicillin, cefotaxime and trimethoprim against E. coli , P. aeruginosa , S. aureus and S. epidermidis had a synergy of 1-fold to 10-folds. In addition, synergy was observed between AgNPs, essential oil (EO) of C. damascena and either amoxicillin, ampicillin, trimethoprim or nitrofurantoin against S. epidermidis by 0.7-fold to 3.7-fold and with trimethoprim against P. aeruginosa , increased the IFA by 1.3-fold. Gentamicin led to the greater enhancement in the IFA up to 9-folds. Moreover, effective synergy was seen between EO of C. damascena and either gentamicin or amoxicillin against E. coli by 11.3-fold and 3.7-fold, respectively, whereas amoxicillin against P. aeruginosa and S. epidermidis by 11.25-fold and 1.8-fold IFA, respectively. The results of this study may lead to the new concepts of antibacterial agents that could contain nanoparticles (NPs) or containing new substances that are likely to have extensive synergy of antibiotics with NPs and essential oils for medicinal plants.