Production of extracellular enzymes by Microsporum canis and their role inits virulence

Microsporum canis is the most prevalent dermatophyte of domestic animals. S everal enzymes produced by dermatophytes, particularly keratinases, are con sidered to play a role in the virulence of this fungus. To investigate the possible relationship between the clinical status of M. canis infection and enzymatic activity of isolates, we studied the relationship between kerati nase, elastase, lipase and DNase levels produced in vitro by different isol ates and virulence as expressed in a guinea pig model. Samples isolated fro m symptomatic dogs and cats showed a statistically significantly (P<0.05) h igher keratinase activity than samples isolated from asymptomatic animals. Experimental infection of guinea pigs showed that a strain with high in vit ro keratinase activity induced acute infection, which resolved clinically a nd mycologically faster than the infection induced by a strain with low ker atinase activity. This suggested a strong correlation between high keratina se activity and the development of symptoms. The same correlation was not o bserved for other enzymes tested.