Adherence of Pityrosporum orbiculare to human stratum corneum cells.

This investigation demonstrates the capacity of Pityrosporum orbiculare to adhere to human stratum corneum cells in vitro; this may be an important initial step in its colonization of stratum corneum. Adherence was significantly higher when incubation for 120 min (mean 9.4 adherent yeasts) was compared to 60 min (mean 3.5 adherent yeasts, P less than 0.001), but not to 90 min (mean 8.6 adherent yeasts, P greater than 0.05). Adherence was higher at an incubation temperature of 37 degrees C (mean 10.0 adherent yeasts) as compared with 25 degrees C (mean 4.0, P less than 0.001), but not at 32 degrees C (mean 8.0, P greater than 0.1). There was no significant difference in adherence related to the anatomic area (forearm, back, and chest) from which the stratum corneum cells have been collected. No difference was seen in adherence between different Pityrosporum strains, but it increased significantly with inoculum size of P. orbiculare, being optimal at 10(7) cells ml-1. The adherence of P. orbiculare and Staphylococcus epidermidis to stratum corneum cells was not influenced by incubation of the organisms together or alone. This model opens possibilities to study the influence of: stratum corneum cells from diseased skin compared with controls; antibodies; and types of surface receptors and antimycotics on P. orbiculare adherence to stratum corneum cells.