Abstract
Staphylococcus aureus is the causative agent of zoonotic diseases that are of increasing epidemiological importance and have significant implications for public health. One hundred fifty ready-to-eat meat product samples were collected from local shops in Qena City, Egypt, to investigate the bacteriological profile of S. aureus and evaluate the antimicrobial effects of marine algal extracts against identified S. aureus isolates in vitro. S. aureus was detected in 30.7% of the samples examined, with the highest incidence in luncheon samples. Detection of virulence genes revealed that 58.7%, 47.8%, 0%, 13%, and 0% of S. aureus isolates harbored coa, nuc, sea, seb, and sec genes. S. aureus isolates demonstrated a high level of antimicrobial resistance. Genetic analysis of antimicrobial resistance determinants revealed that 65.2% of the isolates carried the mecA gene, 72.2% harbored the vanA gene, and 33.3% contained the optrA gene. These findings indicate a significant prevalence of genetic markers associated with resistance to methicillin, vancomycin, and oxazolidinones, respectively, among the studied S. aureus isolates. In addition, these isolates produced various biofilm phenotypes. The most-produced biofilm phenotype was strong (32.6%). Luncheon meat showed the highest MRSA confirmation rate (36.4%), followed by sausage (37.5%), while burger products had the lowest confirmation rate (25.0%). Halimeda opuntia, Jania rubens, and Caulerpa racemosa marine algal extracts' antimicrobial activity was studied. The major constituent of Caulerpa racemosa extract was spathulenol, and the methanol extract of Caulerpa racemosa (1.5 mg/ml) exhibited the strongest antimicrobial activity against S. aureus. RT-PCR revealed significant downregulation of coa (98.7% reduction) and nuc (68.8% reduction) in Caulerpa racemosa extract-treated S. aureus. Algal extracts present a hopeful prospect for developing innovative antibacterial substances with great promise for application in food preservation and medicine.