Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 2 2025 04 05 312 320 Samira Karzani Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Aghil Sharifzadeh Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Bahar Nayeri-Fasaei Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Ali Reza Khosravi Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Jalal Hassan Department of Comparative Bioscience, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Aram Sharifi Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran Ali Pourshaban Shahrestani Department of Comparative Bioscience, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran 2024 11 12 2025 03 08 Background and Objectives: The rising prevalence of antibiotic resistance and biofilm-associated infections poses significant challenges in clinical settings. This study investigates the antimicrobial and anti-adhesive properties of oleuropein, a compound derived from olive leaves, against Candida albicans and Staphylococcus aureus. Materials and Methods: This study was conducted on Candida albicans (fluconazole-resistant/susceptible) and Staphylococcus aureus (methicillin-resistant/susceptible). The antifungal, antibacterial, anti-adhesion, and cell surface hydrophobicity (CSH) effects of oleuropein were evaluated. The impact of oleuropein on germ tube formation (GTF) in C. albicans was assessed. Finally, the toxicity of oleuropein was evaluated in zebrafish embryos. Results: Oleuropein exhibited MIC values of 10 mg/ml for C. albicans and 5 mg/ml for S. aureus. It significantly (P< 0.05) reduced the adhesion of both microorganisms in a dose-dependent manner, with inhibition percentages of 78.43% and 75.91% for C. albicans and S. aureus, respectively. Additionally, oleuropein reduced the CSH of C. albicans, indicating its potential to interfere with adhesion mechanisms. In addition, oleuropein exhibited inhibition of GTF in C. albicans. Conclusion: Oleuropein demonstrates significant antimicrobial and anti-adhesive properties against C. albicans and S. aureus, indicating its potential as a therapeutic agent for preventing biofilm-related infections. However, careful dosage management is crucial due to its observed toxicity at higher concentrations. https://ijm.tums.ac.ir/index.php/ijm/article/view/5130 https://ijm.tums.ac.ir/index.php/ijm/article/download/5130/1771