Resistance Modulation of Staphylococcus aureus Isolates of Dairy Cattle through Metallic Oxide Nanoparticles

The rise in prevalence and drug resistance in Staphylococcus aureus of dairy animals require an alternative to antibiotics. Nanoparticles particularly metallic nanoparticles are a wise approach to modulating drug resistance. The current study thus focuses on the replacement of antibiotics with ZnO, MgO, and Fe2O3 nanoparticles. To achieve this goal, 200 cattle milk samples were collected aseptically and screened for subclinical mastitis using the purposive sampling technique. Following Bergey's manual of determinative bacteriology, S.aureus was identified and antibiotic susceptibility was tested using clinical laboratory and standard institute guidelines. On the other hand, resistant strains were put to antibacterial testing assay against metallic nanoparticles both by well diffusion and broth microdilution method. To analyze the data, both probability and non-probability statistical tools were applied using SPSS version 22 of statistical software at 5% probability. The current study showed 24.56% of S. aureus positive from commercial dairy while the resistance of these isolates against gentamicin, enrofloxacin, levofloxacin, and vancomycin was found to be 50, 40, 30, 30%, respectively. On the other hand, a disc diffusion assay was concluded with 24.525 & PLUSMN;0.806 mm (ZnO) followed by 16.475 & PLUSMN;0.950mm (MgO) and 13.150 & PLUSMN;1.392mm (Fe2O3). MgO stood first to contribute lowest Minimum inhibitory concentration (MIC) (1.302 & PLUSMN;0.564 mg/ mL) followed by Fe2O3 (2.930 & PLUSMN;1.691 mg/mL) and ZnO (3.906 & PLUSMN;0.000 mg/mL). MIC of ZnO was recorded to be 18.23 & PLUSMN;11.93 mg/mL, 15.63 & PLUSMN;0.0 mg/mL, 13.02 & PLUSMN;4.5 mg/mL, 7.81 & PLUSMN;6.77 mg/mL, 5.21 & PLUSMN;2.26 mg/mL, and (3.906 & PLUSMN;0.000 mg/mL) at 04, 08, 12, 16, 20 and 24th h of incubation. A similar trend was followed by other nanoparticles at different hours of incubation. The study thus concludes a rise in resistant strains of S. aureus in bovine milk while metallic nanoparticles as effective alternatives.