Haemolytic activities of Trichophyton species.

Dermatophytes are keratinophilic fungi able to invade the stratum corneum of the skin and other keratinized structures. The pathogenic interactions between host and fungus are poorly understood. Some enzymes, especially keratinases, have previously been taken into consideration as virulence factors. Haemolysins have not been evaluated in this regard, though they are known to play an important role in the host-parasite interaction in bacterial infections. We investigate the haemolytic activity of four Trichophyton species: T. rubrum, T. mentagrophytes complex, Tequinum and T. verrucosum. The strains were tested on Columbia agar with 5% blood from horses, cattle and sheep. They show different haemolytic activities. T. rubrum and T. equinum produce a zone of complete haemolysis followed by a small zone of incomplete haemolysis around the colony. T. mentagrophytes and T. verrucosum produce a zone of complete haemolysis. Haemolytic activity is pronounced in dermatophytes and may play an important role as a virulence factor.