Detection of bacteria with molecular methods in prosthetic joint infection: sonication fluid better than periprosthetic tissue

Background and purpose — The correct diagnosis of prosthetic joint infection (PJI) can be diffi cult because bacteria form a bio- fi lm on the surface of the implant. The sensitivity of culture from sonication fl uid is better than that from periprosthetic tissue, but no comparison studies using molecular methods on a large scale have been performed. We assessed whether periprosthetic tissue or sonication fl uid should be used for molecular analysis. Patients and methods — Implant and tissue samples were retrieved from 87 patients who underwent revision operation of total knee or total hip arthroplasty. Both sample types were ana- lyzed using broad-range (BR-) PCR targeting the 16S rRNA gene. The results were evaluated based on the defi nition of peripros- thetic joint infection from the Workgroup of the Musculoskeletal Infection Society. Results — PJI was diagnosed in 29 patients, whereas aseptic failure was diagnosed in 58 patients. Analysis of sonication fl uid using BR-PCR detected bacteria in 27 patients, whereas analy- sis of periprosthetic tissue by BR-PCR detected bacteria in 22 patients. In 6 of 7 patients in whom BR-PCR analysis of peri- prosthetic tissue was negative, low-virulence bacteria were pres- ent. The sensitivity and specifi city values for periprosthetic tissue were 76% and 93%, respectively, and the sensitivity and specifi c- ity values for sonication fl uid were 95% and 97%. Interpretation — Our results suggest that sonication fl uid may be a more appropriate sample than periprosthetic tissue for BR-PCR analysis in patients with PJI. However, further investi- gation is required to improve detection of bacteria in patients with so-called aseptic failure.