Synthesis of silver nanoparticles using Nigella sativa seed extract and its efficacy against some multidrug-resistant uropathogens

Abstract

Background: Urinary tract infection (UTI) is one of the most chronic infections in humans, as well as the most common cause of multidrug-resistant (MDR) pathogen emergence, necessitating the quest for stringent antibiotic treatment. In the imperative search for effective drugs to combat MDR, silver nanoparticles (AgNPs) are given priority. The objective of this study was to synthesize, characterize, and evaluate the antimicrobial activity of AgNPs synthesized using Nigella sativa on MDR uropathogens. Methods: Urine samples of suspected UTI patients were collected using sterile sample bottles and cultured on different agar media to isolate and identify uropathogens using conventional method. All isolates were screened for multidrug resistance by disk diffusion method following the Clinical and Laboratory Standards Institute guideline with slight modification. N. sativa seed extract was used to synthesize AgNPs from aqueous solution of silver nitrate (AgNO3). AgNPs formed were characterized using ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscope (SEM), dynamic light scattering, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy (XRD). Antibacterial activities of synthesized AgNPs were assessed (in vitro) by disc diffusion method against MDR isolates, and cytotoxicity was evaluated using brine shrimp lethality assay. The formed AgNPs were characterized using UV-Vis, and antibacterial activity of synthesized AgNPs was assessed (in vitro) by impregnated disc diffusion method against MDR isolates. Results: Escherichia coli, Klebsiella sp., and Staphylococcus aureus were isolated. Multiple antibiotic-resistant indexes of the isolates ranged between 0.4 and 0.75 against the different standard antibiotics tested. The color change from pale yellow to dark brown was indicative of AgNP formation. UV-Vis spectrum of solution containing AgNPs exhibited peak wavelengths of 378 nm. Fourier transform infrared spectroscopic analysis showed that terpenoids, flavonoid, and phenols played an important role in the biosynthesis. Irregular shapes within nanoscale range were detected using SEM. XRD showed that the particles were crystalline in structure with an average size of 32 nm. The mean diameter zone of inhibition (in mm) for the different isolates at the dose of 100 μg/mL concentration showed maximum for E. coli (18 mm) followed by both Klebsiella sp. and S. aureus at 17 mm. Conclusion: The study underscores the efficacy of the plant-mediated nanoparticles as well as their potential for use as broad-spectrum antimicrobial agents for the management of MDR uropathogens.