Although prosthetic joint infection (PJI) is a rare event after arthroplasty, it represents a significant complication that is associated with high morbidity, need for complex treatment, and substantial healthcare costs. An accurate and rapid diagnosis of PJI is crucial for treatment success. Current diagnostic methods in PJI are insufficient with 10–30% false-negative cultures. Consequently, there is a need for research and development into new methods aimed at improving diagnostic accuracy and speed of detection. In this article, we review available conventional diagnostic methods for the diagnosis of PJI (laboratory markers, histopathology, synovial fluid and periprosthetic tissue cultures), new diagnostic methods (sonication of implants, specific and multiplex PCR, mass spectrometry) and innovative techniques under development (new laboratory markers, microcalorimetry, electrical method, reverse transcription [RT]-PCR, fluorescence in situ hybridization [FISH], biofilm microscopy, microarray identification, and serological tests). The results of highly sensitive diagnostic techniques with unknown specificity should be interpreted with caution. The organism identified by a new method may represent a real pathogen that was unrecognized by conventional diagnostic methods or contamination during specimen sampling, transportation, or processing. For accurate interpretation, additional studies are needed, which would evaluate the long-term outcome (usually >2 years) with or without antimicrobial treatment. It is expected that new rapid, accurate, and fully automatic diagnostic tests will be developed soon.

The role ofPropionibacterium acnesin acne and in a wide range of inflammatory diseases is well established. However,P. acnesis also responsible for infections involving implants. Prolonged aerobic and anaerobic agar cultures for 14 days and broth cultures increase the detection rate. In this paper, we review the pathogenic role of P. acnes in implant-associated infections such as prosthetic joints, cardiac devices, breast implants, intraocular lenses, neurosurgical devices, and spine implants. The management of severe infections caused byP. acnesinvolves a combination of antimicrobial and surgical treatment (often removal of the device). Intravenous penicillin G and ceftriaxone are the first choice for serious infections, with vancomycin and daptomycin as alternatives, and amoxicillin, rifampicin, clindamycin, tetracycline, and levofloxacin for oral treatment. Sonication of explanted prosthetic material improves the diagnosis of implant-associated infections. Molecular methods may further increase the sensitivity ofP. acnesdetection. Coating of implants with antimicrobial substances could avoid or limit colonization of the surface and thereby reduce the risk of biofilm formation during severe infections. Our understanding of the role ofP. acnesin human diseases will likely continue to increase as new associations and pathogenic mechanisms are discovered.