sentences:  The anaerobic bacterial species "Cutibacterium acnes" (formerly "Propionibacterium acnes") contributes to the development of acne, but its exact role is not well understood.There are specific sub-strains of "C. acnes" associated with normal skin and others with moderate or severe inflammatory acne.It is unclear whether these undesirable strains evolve on-site or are acquired, or possibly both depending on the person.