Diversity and Antifungal Susceptibility of Malassezia spp. Isolated From Brazilian Patients With Pityriasis Versicolor and Seborrheic Dermatitis

TL;DR

This study analyzed Malassezia species in Brazilian patients with skin conditions and found varying antifungal resistance levels.

Contribution

The study reports the first identification of rare Malassezia species in Brazil and their antifungal susceptibility profiles.

Findings

M. furfur was the most common species among Brazilian patients with PV and SD.

All isolates showed high resistance to caspofungin and isoconazole.

Itraconazole and ketoconazole were the most effective antifungals tested.

Abstract

Malassezia spp. are part of the microbiota of many animals, including humans. However, under certain conditions, they can become pathogenic. Diseases associated with Malassezia include pityriasis versicolor (PV), seborrheic dermatitis (SD), Malassezia folliculitis, atopic dermatitis, psoriasis and fungemia.

The present study aimed to describe the distribution of Malassezia species among Brazilian patients with PV and SD and to evaluate their susceptibility profiles to common antifungals.

In this study, 102 clinical samples from patients with PV or SD were analysed. Clinical isolates of Malassezia were identified at the species level by sequencing the D1/D2 variable domains of the large subunit rRNA gene. Antifungal susceptibility was assessed using a modified microbroth dilution method adapted for the growth of Malassezia species.

Among the 40 cultures obtained, six Malassezia species were identified. M. furfur was the most prevalent species (40.0%), followed by M. sympodialis (27.5%),
M. globosa
(15.0%),
M. japonica
(7.5%) and both M. yamatoensis and M. slooffiae (5.0% each). All isolates exhibited high MICs to caspofungin (> s16 μg/mL) and to isoconazole (MIC₅₀ = 8 μg/mL). Miconazole and clotrimazole showed MIC₅₀ values of 4 μg/mL, while itraconazole and ketoconazole were more active, with an MIC₅₀ of 0.125 μg/mL.

This study showed the diversity of Malassezia species causing PV and SD in Brazil, including the rare species M. yamatoensis and
M. japonica
. These findings highlight the importance of antifungal susceptibility testing for these species to guide appropriate therapy.