Propionibacterium acnes is an emerging pathogen especially in orthopedic implant infection. Aim of this study was to investigate P. acnes phylogeny and to screen for virulence factors among a large collection of clinical isolates involved in spine material infections, arthroplasty infections and acne lesions. 88 P. acnes clinical isolates were collected between January 2003 and December 2014 at Nantes University Hospital (France). Fifty-eight isolates came from spine infections, 14 from prosthetic infections (knee, hip or shoulder), 14 from acne lesions and two reference strains (ATCC11827 and ATCC6919). Implant associated infections were confirmed using Infectious Diseases Society of America criteria for bone and joint infections. Phylotypes and Multi-Locus Sequence Typing (MLST) was carried out on all isolates as described by Lomholt et al. All isolates were tested by established PCR-based assays for 21 putative virulence factor genes characteristic of P. acnes. MLST analysis revealed an association between clonal complexes (CCs) and origin of P. acnes isolates (p = 0,027). Regarding CCs distribution between different origins, CC36 and phylotype II P. acnes isolates are more frequently observed in prosthetic joint infections. On the other hand, CC18 (IA) and CC28 (IB) P. acnes isolates are more frequently involved in spine infections and acne lesions. Among all virulence factors screened, hyaluronate lyase gene was only present in CC36 and phylotype II P acnes isolates. Other virulence factors were present in all isolates, whatever their origin or CC. Regarding molecular typing results, P. acnes involved in spine infections seem to have a skin origin (same CC as isolates from acne lesion). Interestingly, the origin of prosthetic joint infection isolates seems different and they all carry one more virulence factor. Hyaluronate lyase (Hyl) is a major surface protein of P. acnes with potential antigenetically variable properties that might be essential for P. acnes virulence. Increased tissue permeability caused by the action of hyaluronidase on the extracellular matrix appears to play a role in wound infections, pneumonia, and other sepsis such as bacteremia and meningitis. It could be also take a prominent part in P. acnes prosthetic joint infection pathogenesis.
