Inhibitory activity of silver nanoparticles on staphylococcus aureusgrowth and α-hemolysin gene expression

This study aimed to isolate S. aureus from clinical samples, synthesize silver nanoparticles, and evaluate their antibacterial activity against S. aureus, as well as their ability to inhibit the expression of the α-hemolysin virulence gene. A total of 250 clinical samples were collected, including urine, burns, and sputum samples. Culturing, biochemical tests, the API20 assay, the Vitek2 system, and PCR were used to identify S. aureus isolates. Silver nanoparticles (AgNPs) were synthesized by the chemical reduction method and characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FT-IR). Antibacterial activity was measured by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and agar-well diffusion assay. Real-time PCR was used to evaluate the effect of AgNPs on α-hemolysin gene expression. Out of 250 samples, 44 (17.6%) were positive for S. aureus. There was no significant difference in isolation rates between sample types, genders, or age groups. AgNPs showed good antibacterial activity with inhibition zones up to 14.41 mm and MIC and minimum bactericidal concentration values of 8 and 64 μg/mL, respectively. Exposure to AgNPs significantly downregulated S. aureus α-hemolysin gene expression compared to untreated controls. To find out how AgNPs affected the production of virulence factors, real-time PCR was used to measure the levels of expression of the HLA gene that codes for α-hemolysin before and after being exposed to nanoparticles. The results showed that AgNPs significantly decreased HLA expression in S. aureusisolates compared to controls that were not treated. This indicates the ability of AgNPs to suppress virulence in addition to their antibacterial effects. Finally, chemically synthesized AgNPs showed strong antibacterial and antivirulence properties against clinical S. aureus isolates, which shows how useful they could be as a medicine. The results warrant further studies into the exact mechanisms of AgNP antibacterial and antivirulence action. Overall, this study demonstrates the promise of AgNPs as a treatment approach for S. aureus infections.