ROS Mediated Cytotoxicity Exhibited by Cashewnut Shell Extract Coated AgNPs Against Staphylococcus aureus Isolated from Milk

This work aimed to synthesize silver nanoparticles (AgNPs) using cashewnut shell extract (CNSE) and evaluate its antibacterial and anti-biofilm activities against Staphylococcus aureus. CNSE showed the presence of isorhamnetin as the major phytochemical compound. The size, shape, morphology and stability of synthesized CNSE-AgNPs were investigated using ultraviolet-visible spectroscopy (peak at 433 nm), zeta potential (- 24.2 mV), field emission scanning electron microscopy (89.1-100.8 nm) and transmission electron microscopy (Spherical shape with diameter of 3-25 nm). X-ray diffraction data indicated the presence of silver in crystalline form (2-theta values of 38, 54 and 77). CNSE-AgNPs showed strong antibacterial activity with zone of inhibition (15 +/- 0.06 to 20 +/- 0.17 mm) and minimum inhibitory concentration (MIC) (7.81-31.25 mu g/ml) against Staphylococcus aureus strains isolated from fresh cow milk samples, methicillin sensitive Staphylococcus aureus (MSSA) (ATCC-25923) and methicillin resistant Staphylococcus aureus (MRSA) (ATCC-700699). CNSE-AgNPs exhibited higher level of nucleotide leakage through membrane disruption (8.97-10.76 folds), reactive oxygen species generation (1.92-3.3 folds), malondialdehyde production (16.85-30.39%) and biofilm inhibition (54.82-78.25%) when compared to untreated Staphylococcus aureus. CNSE-AgNPs was found to effectively eradicate the artificially inoculated Staphylococcus aureus in milk model within 4th h.