In vitro zoosporogenesis among oomycetes Pythium insidiosum isolates

Pythium insidiosum is an aquatic oomycete and the etiology of a chronic disease called pythiosis, commonly found in the skin of horses. The production of mobile zoospores by this microorganism is the determinant factor of this disease. This study evaluated the zoosporogenesis and quantification of zoospores in 32 samples of Pythium insidiosum isolated from horses with pythiosis. The assay used culture of the Pythium insidiosum in Corn Meal Agar plus grass blades for 5 days at 37 degrees C. The gross blades were incubated in Induction Medium at 37 degrees C for 24 hours. The findings showed 16 samples (50%) yielded 20,000 zoospores mL(-1), 12 (37.5%) samples yielded over 20,000 zoospores mL(-1) and 4 samples (12.5%) yielded less than 20,000 zoospores mL(-1). The zoospores production was higher between 6 and 8 hours of incubation. The protocol used in the zoosporogenesis induction was efficient and represents an important tool for Pythium insidiosum identification and the attainment of zoospores in adequate amounts for inoculation in experimental animals and application in the development of susceptibility tests.