Comparison of virulence factors and susceptibility profiles of Malassezia furfur from pityriasis versicolor patients and bloodstream infections of preterm infants.

In spite of the increasing medical interest of Malassezia yeasts, the virulence factors of M. furfur causing blood stream infections (BSI) were never investigated. Therefore, phospholipase (Pz), lipase (Lz), hemolysin (Hz), biofilm production and in vitro antifungal susceptibility profiles were evaluated in M. furfur strains, both isolated from pityriasis versicolor (PV) patients (n = 18; Group 1) or from preterm infants BSI (n = 21; Group 2). All the teststains exhibited Pz activity whereas 92.3% and 97.4% of strains exhibited Lz and Hz activities, respectively. Pz, Lz and Hz activities were higher (i.e., lower values) within Group 1 strains (i.e., 0.48, 0.40 and 0.77) than those within Group 2 (i.e., 0.54, 0.54 and 0.81). The biofilm production was higher within Malassezia isolates from Group 2 (0.95 ±0.3) than from Group 1 (0.72±0.4). Itraconazole and posaconazole were the most active drugs against M. furfur, followed by amphotericin B and fluconazole. The minimum inhibitory concentrations (MIC) values varied according to the origin of M. furfur strains being statistically lower in M. furfur from Group 1 than from Group 2. This study suggests that M. furfur strains produce hydrolytic enzymes and biofilm when causing PV and BSI. Data suggest that the phospholipase activity, biofilm production and a reduced antifungal susceptibility profile might favour M. furfur BSI, whereas lipase and haemolytic activities might display synergic role in skin infection.