Isolation and inhibition of antibiotic-resistant bacteria using silver nanoparticles

Abstract

This study evaluates the antibacterial effect of silver nanoparticles against two clinically significant bacterial species: Escherichia coli and Klebsiella pneumoniae. Bacterial isolates are collected from AlShaheed Ghazi Al-Hariri Hospital for Specialized Surgeries in
Baghdad, and activated using Brain Heart Infusion (BHI) broth. They are then cultured on MacConkey and Nutrient agar media. Both
species have demonstrated lactose fermentation, as evidenced by the change in the MacConkey medium to a pink color. Silver nanoparticles are prepared in four concentrations (0.0100 g, 0.0150 g, 0.0200 g, and 0.0500 g) dissolved in 100 ml of dimethyl sulfoxide (DMSO), and their antibacterial activity is tested by using the well diffusion method. After 24 hours of incubation, E. coli has showed a
clear inhibition zone of 4 cm at the highest concentration, indicating strong sensitivity to the nanoparticles. In contrast, K. pneumoniae has exhibited no inhibition zones at any concentration, suggesting resistance under the same conditions. These findings highlight the species-specific antibacterial activity of silver nanoparticles. The effective inhibition observed against E. coli but not against K. pneumoniae emphasizes the need for further research to optimize nanoparticle formulations or to explore their combined use with antibiotics to enhance antimicrobial efficacy.