Virulence factors in Malassezia species

ANGIOLELLA, LETIZIA; MUSSIN, JAVIER; GRECO, ROSA; SOSA, MARIA DE LOS ANGELES; ROJAS, FLORENCIA; GIUSIANO, GUSTAVO

Congreso; 47° Congresso Nazionale della Società Italiana di Microbiologia; 2019

1.Introduction: Malassezia genus includes a group of lipophilic and mostly lipid-dependent yeasts that are recognized as members of the normal skin mycobiome of both human and other homoeothermic organisms. However, Malassezia species are natural inhabitants of the healthy skin, under certain conditions, they may cause or exacerbate several skin diseases as pitiriasis versicolor (PV) seborrheic dermatitis (SD), and atopic dermatitis (AD). Furthermore, Malassezia species have been associated with systemic infections. Due to its ability to produce superficial and systemic infections in both immunocompromised and immunocompetent hosts, Malassezia is considered an important emerging pathogen. To allow a better knowledge of its pathogenicity, it is important to investigate the expression of some virulence factors. In this study, we evaluated the cellular surface hydrophobicity (CSH) levels, adherence capacity and biofilm formation of 4 Malassezia species frequently involved in various dermatological processes.2. Materials and methods: Twenty-six clinical Malassezia isolates from PV, SD, AD, and health subjects (HS) were studied; 4 M. furfur from lesions and 1 HS, 13 M. sympodialis 8 from lesions and 5 HS, 4 M. globosa 3 from lesions and 1 HS, 2 M. slooffiae from lesions. The adherence capacity was determined polystyrene surface and CSH levels using two-phase system. A semiquantitative measurement of biofilm formation was made by tetrazolium salt (XTT) reduction assay and by Scanning Electron Microscopy (SEM).3. Results. All isolates were hydrophobic and adherent. CSH showed values in a range of 9.8 ± 2.1% to 87.7 ± 15.2%, about 50% of the strains were highly hydrophobic. The adherence was between 15 ± 2.8% to 98.7 ± 3.2%. M. globosa and M. slooffiae showed mayor adherence than M. sympodialis. The average of XTT values were, for M. furfur 0.60 ± 0.3, M. sympodialis 0.464 ± 0.17, M. globosa 0.60 ± 0.05 and for M. slooffiae 0.161 ± 0.13. The averages values obtained for the three virulence factors were high when the strains were isolated in HS respect to isolates in lesions. SEM observations confirmed the biofilms formations characterized by abundant extracellular matrix covering the yeast cells. 4.Discussion and conclusions. Hydrophobicity is an important factor to adherence and to biofilm formation on abiotic surface, this characteristic was present in all isolates studied with different capacity. These important virulence factors can influence the capacity of M. furfur, M. sympodialis, M. globosa, and M. slooffiae to change from commensal to pathogen status. The observed capacity to form biofilms is related to the capacity to colonize catheters and consequently to produce fungemia.