ANTIBACTERIAL PROPERTIES OF SILVER NANOPARTICLES AS A SUBSTITUTE FOR SYNTHETIC ANTIBIOTICS IN POULTRY FARMING

Abstract

The present study investigated the antimicrobial properties of silver nanoparticles (AgNPs) against selected Gram-negative and Gram-positive bacteria using the agar diffusion method. AgNPs were applied at concentrations ranging from 10 to 50 ppm. Tetracycline (45 ppm) served as the positive control, while distilled water was used as the negative control. To determine the minimum inhibitory concentration (MIC), bacterial growth inhibition was evaluated spectrophotometrically by measuring optical density at 600 nm (OD₆₀₀). Statistical analysis was conducted using one-way analysis of variance (ANOVA), followed by Duncan’s multiple range test, with significance established at P < 0.05.
The results demonstrated a pronounced antimicrobial effect of AgNPs against the Gram-negative strains Escherichia coli and Salmonella typhimurium. All tested concentrations (10–50 ppm) significantly suppressed bacterial growth (P < 0.01), and the lowest MIC value was identified as 6.25 ppm, at which OD₆₀₀ values indicated complete inhibition of cell proliferation. In contrast, AgNPs had no significant inhibitory effect (P > 0.05) on the growth of the Gram-positive bacteria Lactobacillus acidophilus and Lactobacillus sp., highlighting the selective nature of their antimicrobial activity.
The observed selectivity suggests that silver nanoparticles can effectively target pathogenic Gram-negative bacteria while preserving beneficial lactic acid microflora. This is particularly relevant for poultry farming and veterinary medicine, where maintaining a balanced gut microbiota is crucial for animal health and productivity. Furthermore, the strong inhibitory action of AgNPs supports their potential as a natural and efficient alternative to conventional synthetic antibiotics. The application of AgNPs at low, biologically safe concentrations may contribute to enhanced biosafety, reduction of antimicrobial resistance risks, and improved microbiological quality of animal-derived products.
Overall, the findings underscore the promise of silver nanoparticles as a multifunctional antimicrobial agent. Their incorporation into feed additives, veterinary preparations, or biosafety protocols could provide an innovative strategy for reducing antibiotic use while supporting sustainable and health-oriented livestock production.