Antibacterial and Antibiofilm Activity of Aqueous Extract of Nigella sativa Silver Nanoparticles against Staphylococcus aureus Isolated from Milk and Dairy Products

Staphylococcus aureus (S. aureus) is a significant microorganism affecting both humans and animals. It has a reputation for being able to generate biofilms, which enhance its resistance for conventional antibiotics. This research was aimed to investigate the potential impact of Silver nanoparticles based on aqueous extract nigella Sativa (Ns-AgNps) against S. aureus isolated from milk and some dairy products (yogurt and kareish cheese) , then evaluate their biofilms formation. The dairy samples were collected from September (2022) to January (2023), with overall amount of (100) samples, including (54) raw milk, (24) yoghurt, and (22) kareish cheese, the samples collected from local markets at El Quanater El Khairiya city , Egypt. The results showed a prevalence of S. aureus 29.6% in raw milk, 9.09% in karesh cheese and 8.33% yogurt. the isolated S. aureus isolates was assessed using a microtiter plate test for the formation of biofilms. resulted in (45%) non biofilm formers and (55%) weak biofilm formers.The outcomes demonstrated that the lowest concentration that inhibits bacterial growth (MIC) using Ns-AgNps was ranged between (3.125-50 μg/mL) plating them showed no bacterial growth which indicated the same values for minimum bactericidal concentration (MBC) .Also, antibiofilm reduction rate on 20 S. aureus isolates using tissue culture plate assay ranging from 20.20 % up to 93.20%.The results could open avenues for the creation of alternative antimicrobial and antibiofilm using natural extracts and nanoparticles, ultimately enhancing food safety and public health.