Background and Aim: Bovine mastitis is the costliest prevalent disease in the dairy sector due to the limitations of conventional treatments. Zinc oxide nanoparticles (ZnO-NPs) have been regarded as safe and economical antibacterial candidates against several microorganisms, but the tendency of these particles to aggregate is a major barrier to their application. This study aimed to enhance the antibacterial efficiency of ZnO-NPs against some bacterial agents, causing bovine mastitis.

Materials and Methods: A total of 24 milk samples out of 300 cases from Nubaria farm, Beheira Governorate, Egypt, were collected from cows with clinical mastitis. ZnO-NPs were fabricated by a sonochemical method using starch as a capping agent and by an auto-combustion reaction using glycine as a fuel. The two preparations of synthesized ZnO-NPs at different concentrations were assessed for their antimicrobial activities in vitro against Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae isolated from milk of affected cows.

Results: Sonochemically synthesized capped ZnO-NPs were dispersed and non-agglomerated in comparison with aggregated uncapped ZnO-NPs prepared by an auto-combustion reaction. Capped dispersed ZnO-NPs showed higher antibacterial activity against S. aureus, E. coli, and K. pneumoniae than particles synthesized by the auto-combustion reaction at same concentrations. However, the zone of inhibition for dispersed and agglomerated ZnO-NPs was concentration-dependent. In addition, Gram-positive S. aureus exhibited higher resistance to ZnO-NPs synthesized by both methods than Gram-negative E. coli and K. pneumoniae.

Conclusion: Dispersed, non-agglomerated ZnO-NPs fabricated using starch as a capping agent under sonochemical irradiation could potentially be regarded as highly effective and inexpensive antimicrobial agents against S. aureus, E. coli, and K. pneumoniae for the management of bovine mastitis.

Keywords: antibacterial activity, clinical mastitis, dairy cows, zinc oxide nanoparticles.