Improved diagnosis of periprosthetic joint infection by multiplex PCR of sonication fluid from removed implants

Abstract

The microbiological diagnosis of periprosthetic joint infection (PJI) is crucial for successful antimicrobial treatment. Cultures have limited sensitivity, especially in patients receiving antibiotics. We evaluated the value of multiplex PCR for detection of microbial DNA in sonication fluid from removed orthopedic prostheses. Cases of PJI in which the prosthesis (or part of it) was removed were prospectively included. The removed implant was sonicated, and the resulting sonication fluid was cultured and subjected to multiplex PCR. Of 37 PJI cases (17 hip prostheses, 14 knee prostheses, 4 shoulder prostheses, 1 elbow prosthesis, and 1 ankle prosthesis), pathogens were identified in periprosthetic tissue in 24 (65%) cases, in sonication fluid in 23 (62%) cases, and by multiplex PCR in 29 (78%) cases. The pathogen was detected in 5 cases in sonication fluid only (Propionibacterium acnes in all cases; none of these patients had previously received antibiotics) and in 11 cases by multiplex PCR only (all of these patients had previously received antibiotics). After exclusion of 8 cases caused by P. acnes or Corynebacterium species, which cannot be detected due to the absence of specific primers in the PCR kit, sonication cultures were positive in 17 cases and multiplex PCR sonication cultures were positive in 29 cases (59% versus 100%, respectively; P < 0.01). Among 19 cases (51%) receiving antibiotics, multiplex PCR was positive in all 19 (100%), whereas sonication cultures grew the organism in 8 (42%) (P < 0.01). Multiplex PCR of sonication fluid is a promising test for diagnosis of PJI, particularly in patients who previously received antibiotics. With modified primer sets, multiplex PCR has the potential for further improvement of the diagnosis of PJI.

FIG. 1.

Sensitivity of culture and multiplex PCR of sonication fluid. The sensitivity values are shown overall (all cases) and stratified according to patients who had received antimicrobial therapy previously (n = 19) and patients who had not received antimicrobial therapy (n = 18). Eight pathogens (7 Propionibacterium acnes and 1 Corynebacterium species) were missed by multiplex PCR due to lack of specific primers for these species. The value at the bottom of each bar indicates the number of PJI cases in that group, and the percentage above each bar indicates the sensitivity. NS, not significant.

FIG. 2.

Serial determinations of DNA quantity by multiplex PCR according to the duration of antibiotic treatment in three patients. The quantity of DNA by multiplex PCR is expressed as H values on the y axis. The infecting microorganism was S. aureus in 2 cases and S. epidermidis in 1 case. Note that the H value is a measure of DNA quantity, defined as the integral of the fluorescence intensity and a semiquantitative measure of the initial quantity of target DNA.