Antibacterial effect of silver nanoparticles along with protein synthesis-inhibiting antibiotics on Staphylococcus aureus isolated from cattle mastitis

Introduction: staphylococcus aureus is an opportunistic pathogen in dairy ruminants which is also found in healthy carriage and can be a major cause of mastitis. various mastitis control programs have been used to combat the problem but have not always been efficient. in most countries, antibiotic resistance is extremely common. silver nanoparticles have shown antimicrobial activity against s. aureus. in the present study the effect of silver nanoparticles on s. aureus isolated from cattle mastitis along with antibiotics of operative on protein bacterial synthesis investigated. materials and methods: three hundred eleven milk samples were collected from the cow farms. each milk sample was cultured on mannitol salt agar and was incubated. a total of 72 isolates of s. aureus were isolated from the bovine mastitis milk samples. s. aureus dna extracted by dna purification kit according to the manufacturer protocol. 58 isolates were confirmed as s. aureus by biochemical tests as well as nuc gene detection. mic and mbc determined for silver nanoparticles with antibiotics on 50 isolates. results: the resistance of s. aureus isolates against erythromycin, gentamicin, streptomycin and doxycycline were 100, 22, 100 and 8%, respectively. 8 of all isolates were sensitive to 25 µg/ml concentration of silver nanoparticles. the 92% growth of the samples were inhibited at concentrations between 50-100 µg/ml. discussion and conclusion: the present study suggests that antibiotics which can inhibit protein synthesis have significant synergistic effect along with silver nanoparticles.