[en] BACKGROUND: Microsporum-canis-infected cats, especially the asymptomatic infected ones, are mainly responsible for the zoonotic disease. The important variability of the clinical signs in cats is poorly understood. Recently, a 31.5-kD keratinolytic subtilase was found to be a putative virulence factor. OBJECTIVE: To investigate the possible relationship between the clinical status of dermatophytic cats and the production of the keratinase. METHODS: Seven M. canis strains isolated either from clinically affected, asymptomatic infected or mechanical carrier cats were tested for the in vitro production of the enzyme. The immunohistochemical detection of the enzyme was also assessed in skin biopsies of 4 symptomatic and 7 asymptomatic naturally infected cats. RESULTS: All the strains produced in vitro a 31.5-kD keratinolytic subtilase. The enzyme was present in all but 1 of the infected cats. CONCLUSION: The production of the keratinase is not a factor directly responsible for the clinical picture seen in M.-canis-infected cats.