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Objective To evaluate the usefulness of a multiplex polymerase chain reaction (PCR) assay as a complementary tool in the diagnosis of prosthetic joint infections in the routine setting of a clinical microbiology laboratory, with a special focus on patients at high risk of culture‐negative infections and high suspicion of infection. Methods The results obtained in the routine care setting with the use of the commercial multiplex PCR (Unyvero i60©, Curetis AG, Holzgerlingen, Germany) were retrospectively reviewed. The test was performed in samples of patients with suspected prosthetic joint infection, which were also processed for conventional diagnostic methods, including sonication of the implant when possible. Patients selected for the test were those with negative cultures after a 24‐h incubation period. Results Ninety‐nine PCRs were performed, 57 of which were diagnostic of infection according to 2018 MSIS criteria. Nine patients received antibiotics within the 15 days prior to the diagnostic procedure. Tested samples included synovial fluid (33), sonication fluid (56) and tissue biopsies (10). The PCR test detected microorganisms in 26 samples: including two cases of polymicrobial infection. Eleven patients were diagnosed by using PCR only. The most frequently detected microorganism in PCR was Coagulase‐Negative Staphylococcus in 11 samples, followed by Staphylococcus aureus in five. One sample was positive for the bacteria universal primer, included in the 2.0 version of the kit. Only one discrepancy was detected between a negative PCR and a positive culture. One sample was also positive for a resistance marker (detection of mecA gene in a case of methicillin‐resistant S. aureus infection). Conclusion The incorporation of the Unyvero ITI multiple PCR technique in patients selected by clinical experts is a useful tool for the diagnosis of bone and joint infections in a routine care setting. A close clinical‐microbiological collaboration improves the usefulness of this kit for the management of patients with these infections.

One of the most commonly used treatments for acute prosthetic joint infection (PJI) is DAIR (debridement, antibiotics and implant retention), which comprises the debridement and the retention of the implant, followed by antibiotic treatment. The efficacy of DAIR remains unclear, as the literature has demonstrated variable success rates, ranging from 26% to 92%. The Staphylococcus aureus is one of the most closely related causative microorganisms, especially with acute and late-acute PJI; it has been identified as one of the most significant predictors of DAIR failure. The current guidelines consider the use of vancomycin as the therapy of choice, but it requires the close control of possible side effects. The aim of this study is to determine if a new combination of antibiotics (a highly bactericidal initial combination followed by an antibiofilm scheme) decreases the failure of DAIR-treated acute prosthetic joint infection (PJI) caused by Staphylococcus aureus. A retrospective analysis of cases of orthopedic infections during a nine-year period (2011–2019) was performed. A total of 45 acute PJI cases caused by S. aureus were diagnosed. The results of two antibiotic schemes were compared: a novel scheme comprising 5 days of daptomycin (10 mg/kg/24 h) + cloxacillin (2 g/6 h) followed by levofloxacin (500 mg/24 h) + rifampicin (600 mg/24 h), versus a traditional, less bactericidal scheme of vancomycin (1000 mg/12 h) plus rifampicin (600 mg/24 h) or levofloxacin (500 mg/24 h) plus rifampicin (600 mg/24 h). Twenty-two out of the twenty-four patients treated with the new scheme (91.6%) were free of infection after 24.8 months of mean follow-up, whereas fourteen out of twenty-one patients (66.6%) were free of infection after 46.6 months of follow-up. This difference was statistically significant (p = 0.036). Demographic comparisons demonstrated homogeneous features, except the Charlson score, which was higher in the novel scheme group (p = 0.047). The combination of high-dose daptomycin and cloxacillin, followed by levofloxacin plus rifampicin, together with surgical treatment, shows better results when compared with other antibiotic schemes for treating acute PJI caused by S. aureus in which DAIR was performed.