Cutibacterium acnes (formerly Propionibacterium acnes): friend or foe?

Cutibacterium acnes protects skin homeostasis. The species has three subspecies, and associations between C. acnes subsp. acnes and acne, C. acnes subsp. defendens and prostate cancer, and C. acnes subsp. elongatum and progressive macular hypomelanosis have recently been suggested. Different phylotypes/clonal complexes may cause prosthetic joint and other infections, and virulence factors such as fimbriae, biofilms, multidrug-resistance plasmids, porphyrin, Christie-Atkins-Munch-Petersen factors and cytotoxicity contribute to infections. Isolates are subtyped by multiplex PCR or multi- or single-locus sequence typing; however, these methods could be better synchronized. Resistance of acneic strains to macrolides (25.0-73.0%), clindamycin (10.0-59.0%) and tetracyclines (up to 37.0%) is worrisome, but susceptibility testing is now facilitated by European Committee on Antimicrobial Susceptibility Testing disk diffusion breakpoints. New therapeutic approaches include sarecycline, antimicrobial peptides and bacteriophages. Plain language summary: What is this summary about?: Cutibacterium acnes is necessary for skin health. However, different subspecies and types may be associated with different diseases. At present, the species has three known subspecies and six known major phylotypes. What were the results?: Acne results from a disturbance of the skin bacteria. It has often been linked to C. acnes, whereas associations of other subspecies with prostate cancer, skin disease and various infections have been observed. Strain typing can be performed with different techniques; however, methods should be better synchronized. Resistance of isolates from acne to antibiotics is high. Antibiotic susceptibility testing is necessary and is being facilitated. New treatments with newer antibiotics, antimicrobial peptides and phages are promising. What do the results mean?: C. acnes has three subspecies and numerous types that can support skin health or be linked to different diseases. New associations between different subspecies and prostate cancer, skin disease and infections have been studied. C. acnes resistance to antibiotics is frequent; however, susceptibility testing has already been simplified. Tweetable abstract: Cutibacterium acnessubspecies may be linked to #acne, #sarcoidosis, prostate #cancerand other #diseases. Outcomes depend on subtypes, virulence factors and microbial equilibrium