In vitro, determination of optimal conditions of growth and proteolytic activity of clinical isolates of Trichophyton rubrum

Abstract

Objective To determine the effect of some growth conditions in proteolytic activity of clinical isolates of Trichophyton rubrum. Methods Isolation and identification of a dermatophyte T. rubrum from hair and skin scrapings of patients with dermatophytosis by using the morphological and cultural characteristics. Optimal growth conditions of eight isolates including temperature, pH, culture media type and incubation period were studied, in addition to that the proteolytic activity and its optimal production in liquid media were tested. Results The results showed that the colonies of T. rubrum on Sabouraud dextrose agar (SDA) were like cotton or powder-like, white or light beige, flat or elevated, with or without pigments on the reverse. The optimal conditions of growth were 30°C, pH6 and SDA media. The proteolytic activity against casein as substrate showed that T. rubrum isolates have an ability to produce exocellular protease ranged from 10.5–80.1U/ml according to the source of each isolates. On the other hand, the proteolytic activity varied based on the pH value, temperature, incubation period and concentration of substrate. Conclusion The present data may refer to the vital role of proteolytic activity in the invasion and pathogenesis of T. rubrum infection.

Keywords

• Trichophyton rubrum, growth conditions, proteolytic activity