An in vitro evaluation of antibacterial effect of silver nanoparticles on Staphylococcus aureus isolated from bovine subclinical mastitis
Bovine mastitis is the most costly disease affecting dairy cows and milk production. As Staphylococcus aureus is considered as a major pathogen due to its prevalence in dairy herds, contagious nature of infection, economic impact of treatment and control and its resistance to antimicrobial agents is a well-documented challenge in dairy cows. Therefore, the purpose of this study was to investigate and determine the antibacterial activity of silver nanoparticles against S. aureus isolated from subclinical mastitis cows. The minimum inhibitory concentrations (MIC) distribution of the silver nanoparticles tested for S. aureus field isolates were determined by a broth dilution method. The results show MIC values ranging from 1.25 to 10 μg/ml. The MIC values that inhibited 50 and 90% of the population of the isolates tested of silver nanoparticles were 5 and 10 μg/ml for S. aureus, respectively. In addition, the results of this study demonstrated that the mean time of the antimicrobial action of silver nanoparticles against S. aureus is 7 min. This in vitro result clearly indicates that the silver nanoparticle might have a good activity against S. aureus with mastitis origin.
Key words: Bovine mastitis, silver nanoparticles, Staphylococcus aureus.