Some of the extracts had a good potential for therapeutic uses against some pathogens. It appears that extracts with high antimicrobial activity against Gram-negative bacteria do not necessarily have high activity against other Gram-negative bacteria compared to Gram-positive bacteria. Lilium candidum-mediated silver nanoparticles extract were the most effective plant extracts against the Gram-negative bacteria studied in this work. These plant-mediated silver nanoparticles could be a potential source of new antibacterial agents. Further and more specific studies, in vivo, are recommended to determine the efficacy of these essential oils in the treatment of gram-negative bacterial infections. The data represented in this present study contribute to a novel and unexplored area of nanomaterials as alternative medicine. This study also recommended that it would be important to understand the mode of action of the biosynthesized nanoparticles before their use in nanomedicine applications.