Bactericidal Potency of Green Synthesized Silver Nanoparticles against Waterborne Escherichia coli Isolates

In recent years, silver nanoparticles (Ag NPs) had produced by biological methods such as plant extract due to their efficiency, low cost, being non-toxic, and ecofriendly nature. Ag NPs have antibacterial, anti-mold, and anti-fungi because of their high surface area to volume ratio. In this study, Opuntia ficus-indica (Prickly pear) extract was used to produce green synthesized Ag NPs. Different techniques had adopted to describe the generated nanoparticles, such as an ultraviolet spectrophotometer, Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), and Zeta Potential Analysis. Escherichia coli (E. coli), separated from sediment and water of the Hillah River in Babylon city in Iraq, was utilized to estimate the antibacterial activities of Ag NPs at different concentrations. Both broth microdilution assay and well diffusion assay were applied. The Congo Red Agar implied to investigate the ability of E. coli isolates to form a biofilm. The TEM images of Ag NPs illustrated spherical morphology with a diameter of approximately 22±4 nm. The antibacterial activity tests showed that the Minimum Inhibitory Concentration (MIC) ranged from 0.0125 mg. L^-1 to 0.05 mg. L^-1, whereas Minimum Bactericidal Concentration (MBC) was from 0.025 mg. L^-1 to 0.05 mg. L^-1. Five hours of exposure to the 0.025mg.L^-1 concentrations of the Ag NPs had a bactericidal impact on 92% of the E. coli isolates. In our study, we found silver nanoparticles synthesized by Opuntia ficus-Indica have antibacterial activity against waterborne Escherichia coli isolates and it could be utilized to reduce microbial growth in contaminated water.