The effect of bifonazole on the structure of Trichophyton mentagrophytes.

The morphological changes in the growing hyphae of Trichophyton mentagrophytes treated with a new azole antimycotic bifonazole (Mycospor) were studied by high-resolution scanning electron microscopy. Treatment with the drug at concentrations ranging from 1-10 ng/ml that were much lower than its MIC value for this fungal strain (630 ng/ml) caused a profound inhibition of hyphal growth. It was characterized by several findings: (1) development of wavy or curled hyphae; (2) occasional formation of swollen cells often arranging in chain; (3) partial exfoliation of hyphal walls, and (4) excretion of fibrillar materials. These morphological changes of the hyphae became more prominent with increasing drug concentrations up to 500 ng/ml, at which many hyphae were collapsed and distorted. These results strongly suggest that subinhibitory concentrations of bifonazole profoundly affected the normal growth and induced degenerative changes of the hyphae of T. mentagrophytes probably by affecting some essential metabolism or structure of the fungal cell.