Attenuation of extracellular toxin production in Pseudomonas aeruginosa by green-synthesized nanoparticles

Pseudomonas aeruginosa is a common nosocomial pathogen that causes significant morbidity and mortality, especially among immunocompromised individuals. Its capacity to develop antibiotic resistance presents a significant obstacle in treatment. It generates various extracellular toxins and virulence factors, including alkaline protease, elastase, and phospholipase C, which destroy tissues and encourage bacterial invasion. Other toxins include pyocyanin, a phenazine pigment that may damage membrane proteins, produce oxidative stress, and cause substantial tissue damage. To address this, alternative methods that target virulence factors and toxin production are being investigated. Nanotechnology has emerged as a viable technique for reducing the virulence of P. aeruginosa by decreasing the production of toxins and other pathogenic components. In this study, we manufactured gold (AuNPs), silver (AgNPs), and zinc oxide nanoparticles (ZnONPs) using lactic acid bacteria, specifically Leuconostoc sp. strain C2 and Lactiplantibacillus sp. strain C1. The nanoparticles produced were labeled as C1-AuNPs, C1-AgNPs, C2-AuNPs, and C2-ZnONPs. The nanoparticles exhibited antibacterial activity against P. aeruginosa, with MICs of 1024 µg/mL for C1-AuNPs, 32 µg/mL for C1-AgNPs, and >2048 µg/mL for C2-AuNPs and C2-ZnONPs. C1-AuNPs, C1-AgNPs, C2-AuNPs, and C2-ZnONPs decrease pyocyanin toxin production by 57.75% (at 512 μg/mL), 26.07% (at 16 μg/mL), 71.07% (at 1024 µg/mL), and 82.15% (at 1024 µg/mL). Furthermore, at the sub-MIC level, these nanoparticles limit protease activity in a concentration-dependent manner. The current findings demonstrated that inhibiting the LAB-inspired nanoparticles is a promising technique for reducing their virulence and pathogenicity.

Funding: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea grant funded by the Ministry of Education (RS-2023-00241461).