Biofilms in skin infections: Propionibacterium acnes and acne vulgaris.

It is generally accepted that many human infections are biofilm-related and that sessile (biofilm-grown) cells are highly resistant against antimicrobial agents. Propionibacterium acnes plays a role in the pathogenesis of acne vulgaris, a common disorder of the pilosebaceous follicles and it has been suggested that P. acnes cells residing within the follicles grow as a biofilm. Although P. acnes biofilms have not been observed directly in the pilosebaceous unit, the observation that P. acnes readily forms biofilm in vitro as well as on various medical devices in vivo, combined with the high resistance of sessile P. acnes cells and the increased production of particular virulence factors and qourum sensing molecules in sessile cells point in this direction. In addition, in vitro and in vivo biofilm formation has also been demonstrated for other microorganisms involved in skin diseases (including Staphylococcus aureus and Streptococcus pyogenes).