The factors enabling spp. infections are secretion of hydrolytic enzymes, adherence to surfaces, biofilm formation or morphological transition, and fitness attributes. The aim of this study was to investigate the correlation between known extracellular virulence factors and survival of larvae infected with clinical . The 25 isolates were tested and the activity of proteinases among 24/24, phospholipases among 7/22, esterases among 14/23, hemolysins among 18/24, and biofilm formation ability among 18/25 isolates was confirmed. Pathogenicity investigation using larvae as host model demonstrated that isolates and isolate were the most virulent and isolates were avirulent. virulence was identified as varied, were moderately virulent, and one isolate was of low virulence and the remaining isolates of this species were moderately virulent. According to our study, virulence of isolates is related to the expression of proteases, hemolysins, and esterases.