Evaluation of the antibacterial activities of Ag/ZnO nanoparticles against Streptococcus agalactiae, Staphylococcus aureus and Escherichia coli isolated from infected bovine mammary glands

The objective of this study was to evaluate the antibacterial activity of Ag/ZnO nanoparticles against Staphylococcus aureus, Escherichia coli, and Streptococcus agalactiae isolated from bovine mastitis in dairy cows, both in vivo and in vitro. Ag/ZnO nanoparticles were synthesized by means of the thermal decomposition of oxalate precursors. SEM images revealed that the nanoparticles had a size range of 10-50 nm. A toxicity assessment of nanoparticles conducted using the Artemia salina model indicated that the nanoparticles were not toxic at high concentrations (LD50>6384 μg/ml). A total of 138 mastitic milk samples were cultured to assess the antimicrobial effects of Ag/ZnO NPs. The antimicrobial susceptibility of the isolated bacteria was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill test. To evaluate the efficacy of the treatment, the somatic cell count (SCC), California mastitis test (CMT), and histological tests were employed to assess the cow udders with mastitis that had been treated with Ag/ZnO NPs. The most frequently isolated pathogen was S. agalactiae (50.72%), which demonstrated the highest susceptibility to Ag/ZnO NPs in vitro and in vivo tests.