Potential of biosynthesized nanoparticles as disinfectants against microbial contamination of chicken eggshells

Biosynthesized silver nanoparticles (Ag NPs) exhibit antibacterial activity and can be applied by spraying for the disinfection of the external eggshell surface. This study evaluated the effects spraying of Ag NPs synthesized using Stachys recta L. extract on eggs from Plymouth Rock chickens (Gallus gallus domesticus). Ninety-six fresh eggs were randomly divided into four treatment groups: Ag NPs, AgNO₃, Stachys recta extract, and Virocid, a broad-spectrum disinfectant based on glutaraldehyde and quaternary ammonium compounds. Microbial load was assessed on the eggshell surface before (0 minutes) and after disinfection (1, 5, and 15 minutes). By comparing microbial loads before (0 min) and after disinfection (1, 5, and 15 min), a significant effect of treatment was observed (P < 0.0001). After 15 min of exposure, Virocid achieved complete microbial elimination (3.47 log₁₀ CFU/egg reduction) and was significantly more effective than all other treatments (P < 0.0001). Ag NPs reduced microbial load by 1.34 log₁₀ CFU/egg and were significantly more effective than AgNO₃ (0.39 log₁₀ CFU/egg reduction) and the plant extract (0.20 log₁₀ CFU/egg reduction) (P < 0.0001). By microbiological culture examination of eggshells, we identified 8 bacterial species, Escherichia coli, Enterobacter cloacae, Enterococcus faecalis, Enterococccus faecium, Micrococcus luteus, Staphylococcus aureus, Staphylococcus saprophyticus, and Staphylococcus xylosus. Reducing microbial contamination on the eggshell may help decrease the risk of egg spoilage and microbial penetration. However, the effectiveness of sanitation procedures must also be considered in relation to the preservation of the eggshell cuticle and other natural protective barriers that contribute to egg quality and shelf life.