Recent studies have made it possible to identify 3 subspecies and 6 different phylotypes of the microorganism: C. acnes subsp. defends (type II), C. acnes subsp. elongatum (type III) and Cutibacterium acnes subsp. acnes (type I) divided into phylotypes IA1, IA2, IB, IC. Of particular interest is that type I strains are most often associated with acne vulgaris, while type II strains are more frequently found on healthy skin or in deeper tissue infections. Although the fundamental role of the microorganism in the etiopathology of the disease appears evident at the moment, it remains to be clarified which are the fundamental mechanisms that activate its pathogenicity. Therefore, a study path was undertaken to investigate the relationships of the various C. acnes phylotypes with each other, with the epidermal cells, with the immune system, and with the rest of the skin microbiome in conditions of pathogenicity and not. The research also aims to establish how the various phylotypes of the bacterium affect the severity of the acne manifestation.