Propionibacterium spp. are commensal bacteria that can occasionally cause infectious diseases. The most studied of these infections is
acne vulgaris, caused by
Cutibacterium acnes (formerly
Propionibacterium acnes). It is a chronic inflammatory disease caused by the blockage of pilosebaceous units causing inflammatory lesions, non-inflammatory lesions or a mixture of both on the face, neck and/or chest. Acne vulgaris cannot be defined as an infectious disease since the bacteria is found on a vast majority of individuals without causing lesions. which can later form structures such as closed comedones (white heads) and open comedones.
C. acnes can also produce immune factors such as proinflammatory cytokine inducing-factors and chemotactic factors, and can induce host complement pathways. ==Phylogeny==