The role of molecular diagnostics in implant-associated bone and joint infection.

Microbiological culture is the conventional method for establishing the diagnosis in implant-associated bone and joint infection, but it may lack both specificity and sensitivity. Molecular diagnosis has been an important step in the diagnosis of infectious diseases. We review the principles and the role of molecular diagnosis in improving the aetiological diagnosis of implant-associated bone and joint infection. Currently, molecular diagnosis mainly includes conventional broad-range PCR and specific PCR assays. These tools are efficient, but several pitfalls exist that necessitate rigour in all steps of the process. In implant-associated bone and joint infection, molecular assays have been shown to be useful in complementing culture techniques to identify microorganisms when patients have previously received antibiotics or in the presence of fastidious microorganisms. Broad-range PCR targeting the 16S rRNA sequence followed by sequencing must be performed in culture-negative specimens when infection is suspected on the basis of clinical signs and symptoms or inflammatory syndrome. This molecular tool has allowed not only increasing identification of anaerobic bacteria, such as Finegoldia magna, but also the discovery of the role of Tropheryma whipplei, an aetiological agent of implant-associated bone and joint infection in patients without Whipple's disease. Real-time pathogen-specific PCR assays performed in a closed system are more sensitive and specific than broad-range PCR, but each assay is typically able to detect only a single microorganism. These assays should be performed to confirm the identification provided by broad-spectrum PCR, and also when broad-range PCR fails to detect a microorganism despite efficient DNA extraction.