Antimicrobial Activity of Aqueous Extract from Eurotium cristatum-Fermented Camellia sinensis Tea Against Staphylococcus aureus in Zebrafish Larvae

Abstract

Staphylococcus aureus is a major opportunistic pathogen responsible for various infections in both aquatic and terrestrial organisms. With the growing concern over antibiotic resistance, there is an urgent need to explore alternative antimicrobial agents derived from natural sources. Eurotium cristatum, a beneficial fungal species involved in the fermentation of Camellia sinensis tea, is known to produce bioactive compounds with potential antimicrobial properties. This study evaluates the antimicrobial activity of aqueous extract from Eurotium cristatum-fermented Camellia sinensis tea against S. aureus-induced infections in zebrafish larvae. Zebrafish were exposed to S. aureus (1 × 10⁶ CFU/mL) for 24 hours, followed by treatment with the fermented tea extract at concentrations of 50 μg/mL and 100 μg/mL for another 24 hours. The antimicrobial efficacy of the extract was assessed by analyzing bacterial load reduction, survival rates, and histopathological alterations in zebrafish larvae. Additionally, oxidative stress biomarkers, including reactive oxygen species levels, lipid peroxidation, and nitric oxide production, were quantified. Apoptosis and oxidative stress were further analyzed using acridine orange, diphenyl-1-pyrenylphosphine, and dichlorofluorescein diacetate fluorescence assays. Results showed that the fermented tea extract significantly reduced bacterial load and improved survival rates in zebrafish larvae. The extract also demonstrated potent antioxidative and anti-inflammatory properties by reducing ROS accumulation, lipid peroxidation, and NO production. These findings suggest that bioactive compounds from Eurotium cristatum-fermented tea possess strong antimicrobial and antioxidative effects against S. aureus, making it a promising natural alternative for managing bacterial infections.