Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 18 4 2026 08 04 621 628 Marzieh Halvaeezadeh Department of Medical Mycology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Gholam Ali Jalaee Otorhinolaryngologist, Apadana Hospital, Sorosh Street, Ahvaz, Iran Mahnaz Fatahinia MahnazDepartment of Medical Mycology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Ali Zarei Mahmoudabadi Department of Medical Mycology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 2025 07 12 2026 07 08 Background and Objectives: The ability of Aspergillus species to produce various extracellular enzymes has a pathogenic role in humans. These enzymes not only play a role in metabolism but also act as virulence factors. The secretion of hydrolytic enzymes facilitates tissue invasion and is considered a virulence factor for several fungi. The current study aimed to compare the enzymatic activity of A. flavus section Flavi isolated from otomycosis and environmental samples. Materials and Methods: In the present study, eighty-one isolates of A. flavus including 41 clinical strains from otomycosis and 40 environmental isolates were identified using the calmodulin gene. The enzymatic activity of the isolates was assessed using standard culture media. Results: All isolates exhibited phospholipase and urease activity. Esterase and hemolysin activity in otomycosis isolates were higher than in environmental isolates (88% > 62%), (98% > 72%). High levels of both extracellular and intracellular catalase activity were detected among otomycosis isolates. Conclusion: All isolates were phenotypically identified as Aspergillus section Flavi and then characterized using the calmodulin gene. The mean activity of intracellular catalase enzymes (1.29) in both groups was higher than the mean activity of extracellular catalase enzymes (0.85). Additionally, the esterase (88%) and hemolysin (98%) activity of the clinical isolates was higher than that of the environmental isolates (esterase 62%, hemolysin 72%). All isolates exhibited phospholipase and urease activity. https://ijm.tums.ac.ir/index.php/ijm/article/view/5620 https://ijm.tums.ac.ir/index.php/ijm/article/download/5620/1922