In vivo and in vitro antibacterial effects of nanosilver against Staphylococcus aureus isolated from bovine subacute mastitis

Bovine mastitis is the most costly disease in dairy cows and causes significant decrease in milk production. This disease is one of the main reasons of antibiotic therapy in dairy cows. Staphylococcus aureus is counted as a major pathogen associated with the outbreaks of mastitis in dairy herds. Therefore, the purpose of the present study is to examine the antibacterial activity of nanosilver against Staphylococcus aureus isolated from subacute mastitis in cow. The MIC was calculated by a broth microdilution method, and the MBC was measured by subculturing the bacteria from the wells that showed no apparent growth onto Mueller-Hinton agar. For the in vivo experiment of the current investigation we injected 25 µg/mL of nanosilver for 5 days treat mice contaminated with Staphylococcus aureusisolated from subacute mastitis. The results showed that the MIC and MBC of nanosilver for Staphylococcus aureusisolated from subacute mastitis was 5µg/mL. In addition, the results of the present study demonstrated that the time of the antimicrobial action of nanosilver against Staphylococcus aureus is 7 minutes after adding nanoparticles of silver. Also 5 days treatment with 25 of nanosilver treated contaminated mice with Staphylococcus aureus isolated from subacute mastitis. These in vitro and in vivo results clearly indicate that the nanosilver might have a good antibacterial activity against Staphylococcus aureus.