Itraconazole corneofungimetry bioassay on Malassezia species.

Yeasts of the genus Malassezia are part of the normal skin biocenosis and are involved in a series of distinct skin disorders and specific dermatomycoses in man and animals. Several species are currently distinguished. Their relative in vitro susceptibility to antifungals appears different according to the species and to the nature and route of administration of the drug. Corneofungimetry is an ex vivo bioassay allowing to test the fungal response on human stratum corneum following oral intake of a given antifungal by volunteers. Two series of cyanoacrylate skin surface strippings (CSSS) were harvested from the volar forearm of 30 volunteers before and after a 2-week treatment with itraconazole 200 mg daily. They were coated by olive oil and inoculated with suspensions of seven different Malassezia spp. After a 1-week culture on CSSS, the amount of viable yeasts was assessed using neutral red staining assisted by computerized image analysis. Growth of the seven species was not similar on the CSSS from untreated stratum corneum. The ranking order from the most proliferative to the least was M. restricta, M. sympodialis, M. globosa, M. furfur, M. obtusa, M. slooffiae and M. pachydermatis. Their growth was abated to almost the same level after itraconazole treatment. It is concluded that in vivo treatment with itraconazole is highly active against all Malassezia spp. colonizing the human stratum corneum.