Antibacterial, antivirulant and antioxidant activities of photosynthesized selenium nanoparticles against Escherichia coli isolates

In this study, the antibacterial, antivirulence, and antioxidant properties of photosynthesized selenium nanoparticles (MC-SeNPs) were evaluated against 50 Escherichia coli isolates (33.3%) obtained from 150 clinical samples. Among the isolates, 60% were recovered from urinary tract infections, 30% from wounds, and 10% from burns. Antimicrobial susceptibility testing revealed variable resistance patterns among the isolates. The antimicrobial activity of MC-SeNPs, assessed using a resazurin-based microdilution method, showed minimum inhibitory concentrations (MICs) ranging from 1250 to 312.5 µg/ml. At sub-MIC levels, MC-SeNPs significantly reduced biofilm formation, with inhibition rates ranging from 7.8% to 85% in strong biofilm producers, 44% to 57% in moderate producers, and 39% to 71% in weak producers. Antioxidant activity assays demonstrated a dose-dependent increase in free radical scavenging capacity with Myrtus communis L. leaf extract, MC-SeNPs, and ascorbic acid. Hemolytic activity testing indicated minimal toxicity, as MC-SeNPs exhibited the lowest hemolytic effect even at higher concentrations. Overall, the findings highlight the potential of MC-SeNPs as effective antimicrobial and antivirulence agents with strong antioxidant capacity and low cytotoxicity, suggesting their suitability for diverse medical, industrial, and environmental applications.