Reliability of a multiplex PCR system for diagnosis of early and late prosthetic joint infections before and after broth enrichment.

Early microbiological diagnosis of prosthetic joint infection (PJI) is essential for successful antimicrobial treatment; however, culture has limited sensitivity, particularly in patients who had received antibiotic therapy, and the utility of molecular methods for diagnosing PJIs remains debated. We investigated the reliability of a multiplex PCR system for the microbiological diagnosis of early and late PJIs. Samples of periprosthetic tissues, synovial fluid, and prosthetic implants from 47 patients with early (n=13) or late (n=34) PJI were analyzed by conventional culture and with the multiplex-PCR Unyvero ITI® (U-ITI) cartridge system. Samples treated with dithiothreitol (DTT) and synovial fluids were spread directly on agar plates and inoculated into enrichment broths. The synovial fluids, DTT eluates and enrichment broths were processed according to the U-ITI protocol. When compared against culture as the reference method, U-ITI analysis of DTT eluates had a sensitivity of 34.2%; sensitivity of U-ITI analysis increased up to 81.6% when enrichment broths were analyzed. In particular, sensitivity was 44.4% for synovial fluids, and 41.7%, and 23.5% for DTT eluates from early and late infections, respectively. Sensitivity of analysis of enrichment broths was 83.3% for early infections, 82.3% for late infections and 77.8% for synovial fluids. Our findings seem to suggest that, when coupled with the use of broth culture, U-ITI analysis may allow for more rapid microbial identification than biochemical methods, while no advantages in time to detect microbial growth were observed. Improvements, particularly in sensitivity, are needed to make it more suitable for diagnosis of early and late PJIs.