In vitro susceptibility testing of Pityrosporum ovale against antifungal, antiseborrheic and antipsoriatic agents

Objective The in vitro antimicrobial susceptibility of Pityrosporum ovale strains isolated from patients with seborrheic dermatitis was determined. Method Minimum inhibitory concentrations of a total of 11 agents - including true antifungal, antiseborrheic, and antipsoriatic drugs - were measured. Results Ketoconazole was the most effective of the tested antifungal agents against Pityrosporum ovale in vitro (minimum inhibitory concentration 0.1 μg/ml). The antiseborrheic agents zinc pyrithione and selenium disulfide showed a good in vitro efficacy against Pityrosporum with similar minimum inhibitory concentrations. Liquor carbonis detergens and dithranol were also able to inhibit growth of Pityrosporum ovale in vitro, but much higher concentrations were necessary. Conclusion The tested agents commonly used against seborrheic dermatitis might exert their efficacy, at least in part, due to inhibition of Pityrosporum ovale.