The effect of bifonazole on the structure of Trichophyton

The effect of a new azole antimycotic, 1-[(4-biphenylyl)-phenylmethyl]-1H-imidazole (bifonazole, Bay h 4502, Mycospor) on the morphology of hyphae of Trichophyton mentagrophytes grown in a liquid medium was studied by high-resolution scanning electron microscopy. With bifonazole at concentrations ranging from 1 to 10 ng/ml that were much lower than the MIC value of the drug for this test strain (630 ng/ml), the hyphal growth was significantly inhibited and several morphological changes of the hyphae were produced. They were characterized by: (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 200 ng/ml, and 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 damaging the cell membrane.