Fungal cultures on cyanoacrylate skin surface strippings as a dose-finding method for topical antifungals. A placebo-controlled study with 0.25% and 0.50% itraconazole cream

Corneofungimetry Bioassay on Malassezia spp. under Ketoconazole and Desonide Influences

BACKGROUND

Glucocorticoids can boost some Malassezia-driven dermatoses. However, both antifungals and topical corticosteroids improve lesions of seborrheic dermatitis.

OBJECTIVE

To revisit the topical activity of the antifungal ketoconazole and the corticosteroid desonide on Malassezia growth on human stratum corneum.

MATERIAL AND METHODS

The computer-assisted corneofungimetry bioassay was used to compare the growth of M. furfur, M. globosa and M. restricta on human stratum corneum coated with olive oil. Four blinded gel formulations were tested. They contained either 2% ketoconazole, 0.05% desonide or a combination of 2% ketoconazole and 0.05% desonide; one gel was unmedicated. Untreated stratum corneum and specimens coated with a 2% ketoconazole cream were used as negative and positive comparators, respectively. A total of 45 samples (15 M. furfur, 15 M. globosa, and 15 M. restricta) were used for each test formulation in this randomized, double-blind study.

RESULTS

The 2% ketoconazole gel and cream and the combination of 2% ketoconazole and 0.05% desonide formulation abated similarly and significantly the M. furfur, M. globosa and M. restricta growth. The 3 species were similarly sensitive to these formulations. By contrast, no significant inhibitory effect was yielded by the 0.05% desonide gel and the vehicle.

CONCLUSION

The presence of 0.05% desonide does not impair or improve the Malassezia susceptibility to 2% ketoconazole when growing on lipid-enriched human stratum corneum.

Itraconazole corneofungimetry bioassay on Malassezia species. Itraconazol-Korneofungimetrie-Bioassay an Malassezia-Arten

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.