Malassezia spp. and Candida spp. from patients with psoriasis exhibit reduced susceptibility to antifungals.

Introduction: Psoriasis is a chronic inflammatory disease that affects over 125 million people worldwide. Many studies have shown the importance of the microbiome for psoriasis exacerbation.

Aim: Explore the fungal load and species composition of cultivable yeasts on the skin of psoriatic patients (PP) and healthy volunteers living in a tropical area and evaluate the susceptibility to antifungals.

Methodology: A cross-sectional study with 61 participants (35 patients and 26 healthy controls) was performed during August 2018 and May 2019. Clinical data were collected from patient interviewing and/or medical records review. Samples were collected by swabbing in up to five anatomic sites. Suggestive yeast colonies were counted and further identified by phenotypical tests, PCR-REA, and/or MALDI-TOF. Susceptibility of Malassezia spp. and Candida spp. to azoles, terbinafine, and amphotericin B was evaluated by broth microdilution.

Results: Nearly 50% of the patients had moderate to severe psoriasis, and plaque-type psoriasis was the most common clinical form. Yeast colonies count was significantly more abundant among PP than healthy controls. Malassezia and Candida were the most abundant genus detected in all participants. Higher MIC values for ketoconazole and terbinafine were observed in Malassezia strains obtained from PP. Approximately 42% of Candida isolates from PP showed resistance to itraconazole in contrast to 12.5% of isolates from healthy controls. MIC values for fluconazole and amphotericin B were significantly different among Candida isolates from PP and healthy individuals.

Conclusion: This study showed that Malassezia and Candida strains from PP presented higher MIC values to widespread antifungal drugs than healthy individuals.