Influence of nano bee propolis on methicillin resistant Staphylococcus aureus (MRSA) in yoghurt

Methicillin-resistant Staphylococcus aureus (MRSA) presents a serious public health concern due to its resistance to conventional antibiotics. This study evaluated the antibacterial activity of ethanolic propolis extract and its nanoemulsion (PNE) against MRSA and their application in yogurt as a functional food. S. aureus was isolated from 33.3% (20/60) of yogurt samples and identified using microbiological and biochemical methods. PCR detection of the mecA gene confirmed MRSA in 18 out of 20 isolates (90%), highlighting the reliability of molecular diagnostics. Antibacterial activities of propolis and PNE were assessed by agar well diffusion and minimum inhibitory concentration (MIC) assays. Both showed significant inhibitory effects, with PNE exhibiting superior activity at lower concentrations. Characterisation via dynamic light scattering revealed that PNE had an average droplet size of 123.47 nm and a low polydispersity index (PDI=0.226). MIC for both forms was 0.7%, with complete inhibition observed below this level. Yogurt was fortified with propolis and PNE (0.7%, 1.5%, 3%) and inoculated with MRSA. During 11 days of cold storage, PNE at 3% showed the most effective bacterial reduction. Sensory evaluation by 30 panelists revealed that yogurts enriched with 0.7% propolis and 1.5% PNE maintained high acceptability (scores 4.5 and 4.7, respectively), similar to control sample (4.9). However, higher concentrations of raw propolis reduced acceptability due to bitterness. In conclusion, propolis, particularly in nanoemulsion form, demonstrated strong anti-MRSA activity and potential as a natural preservative in dairy products without compromising the sensory quality.