Developing an in vitro artificial sebum model to study Propionibacterium acnes biofilms

The aim of the present study was to develop a new model system to study Propionibacterium acnes biofilms. This model should be representative for the conditions encountered in the pilosebaceous unit. The new model, consists of an artificial sebum pellet supported by a silicone disc. Sebum pellets were inoculated with various P. acnes strains isolated from both normal and acneic skin. Growth and biofilm formation was verified by conventional plating at different time points, as well as by resazurin assays and fluorescence microscopy after LIVE/DEAD staining. The artificial sebum pellets were also used in assays to measure the production of certain virulence factors implicated in the pathogenesis of acne, including lipase, protease and the presence of CAMP factors. The artificial sebum model can sustain biofilm growth of P. acnes, as was determined by increasing CFU counts for up to 1 week after inoculation. Metabolic activity and biofilm formation were confirmed using resazurin staining and fluorescence microscopy respectively. The production of virulence factors in this model was demonstrated as well.