Sialidase (EC 3.2.1.18) is a pathogenicity factor of many microorganis
ms, and may also play a role in adhesion of dermatophytes to the epith
elia of their hosts by the hydrolytical cleavage of terminal, negative
ly charged sialic acids of glycoconjugates on the cell surfaces, thus
allowing fungal lectins to bind to the subterminal sugars. Therefore,
116 strains of seven species of dermatophytes were investigated for si
alidase production. Two highly sensitive, quantitative sialidase assay
s were applied to cell homogenates and culture supernatants from seven
different media of the fungi, but were always negative for sialidase
activity. However, sialidase activity was always detected in Ophiostom
a stenoceras used as a positive control cultivated in parallel; the en
zyme was inducable by sialylated mucins. A sialidase-dependent pathome
chanism for dermatophytes appears unlikely based on the results presen
ted.