Li C, et al. Hip Pelvis. 2018 Sep;30(3):138-146. https://doi.org/10.5371/hp.2018.30.3.138

The role ofPropionibacterium acnesin acne and in a wide range of inflammatory diseases is well established. However,P. acnesis also responsible for infections involving implants. Prolonged aerobic and anaerobic agar cultures for 14 days and broth cultures increase the detection rate. In this paper, we review the pathogenic role of P. acnes in implant-associated infections such as prosthetic joints, cardiac devices, breast implants, intraocular lenses, neurosurgical devices, and spine implants. The management of severe infections caused byP. acnesinvolves a combination of antimicrobial and surgical treatment (often removal of the device). Intravenous penicillin G and ceftriaxone are the first choice for serious infections, with vancomycin and daptomycin as alternatives, and amoxicillin, rifampicin, clindamycin, tetracycline, and levofloxacin for oral treatment. Sonication of explanted prosthetic material improves the diagnosis of implant-associated infections. Molecular methods may further increase the sensitivity ofP. acnesdetection. Coating of implants with antimicrobial substances could avoid or limit colonization of the surface and thereby reduce the risk of biofilm formation during severe infections. Our understanding of the role ofP. acnesin human diseases will likely continue to increase as new associations and pathogenic mechanisms are discovered.

Background: Determination of alpha defensin in synovial fluid has shown promising results for diagnosing periprosthetic joint infection (PJI). The purposes of our study were to assess the performance of alpha defensin lateral flow (ADLF) test for the diagnosis of acute and chronic PJI using 3 classification systems and to compare its performance with the synovial fluid leukocyte count. Methods: Patients in whom aspiration of a prosthetic hip or knee joint was performed before revision arthroplasty were prospectively included. In addition to standard diagnostic tests, the ADLF test was performed in synovial fluid. Patients were classified as having PJI or aseptic failure according to the definition criteria of the Musculoskeletal Infection Society (MSIS), the Infectious Diseases Society of America (IDSA), and the proposed criteria of the European Bone and Joint Infection Society (EBJIS). The performance of the ADLF test and the leukocyte count was compared using the McNemar chi-square test. Results: Of 212 included patients, 151 (71%) had a knee prosthesis and 61 (29%) had a hip prosthesis. PJI was diagnosed in 45 patients (21%) using the MSIS criteria, in 55 patients (26%) using the IDSA criteria and in 79 patients (37%) using the proposed EBJIS criteria. The sensitivity of the ADLF test was 84% (95% confidence interval [CI], 71% to 94%) with the MSIS criteria, 67% (95% CI, 53% to 79%) with the IDSA criteria, and 54% (95% CI, 43% to 66%) with the proposed EBJIS criteria. The ADLF test showed high specificity using all classification criteria (96% to 99%) and represented the most specific preoperative test for PJI, especially in the early postoperative period (91%; 95% CI, 59% to 100%). Using the proposed EBJIS definition criteria, the sensitivity of the leukocyte count was significantly higher than that of the ADLF test (86% [95% CI, 76% to 93%] compared with 54% [95% CI, 43% to 66%]; p < 0.001), particularly in chronic PJI (81% compared with 44%, respectively; p < 0.001). Conclusions: The ADLF test was rapid and highly specific for diagnosing PJI (>95%). However, its sensitivity was limited (54% to 84%) and it should therefore not be used for screening, but rather as a confirmatory test for PJI. Level of Evidence: Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Increasing antimicrobial resistance reduces treatment options for implant-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the activity of fosfomycin alone and in combination with vancomycin, daptomycin, rifampin, and tigecycline against MRSA (ATCC 43300) in a foreign-body (implantable cage) infection model. The MICs of the individual agents were as follows: fosfomycin, 1 μg/ml; daptomycin, 0.125 μg/ml; vancomycin, 1 μg/ml; rifampin, 0.04 μg/ml; and tigecycline, 0.125 μg/ml. Microcalorimetry showed synergistic activity of fosfomycin and rifampin at subinhibitory concentrations against planktonic and biofilm MRSA. In time-kill curves, fosfomycin exhibited time-dependent activity against MRSA with a reduction of 2.5 log ₁₀ CFU/ml at 128 × the MIC. In the animal model, planktonic bacteria in cage fluid were reduced by 6.0 log ₁₀ with daptomycin-rifampin and fosfomycin-rifampin. Daptomycin-rifampin cured 67% of cage-associated infections and fosfomycin-rifampin cured 83%, whereas all single drugs (fosfomycin, daptomycin, and tigecycline) and rifampin-free fosfomycin combinations showed no cure of MRSA cage-associated infections. No emergence of fosfomycin resistance was observed in animals; however, a 4-fold increase in fosfomycin MIC (from 2 to 16 μg/ml) occurred in the fosfomycin-vancomycin group. In summary, the highest eradication of MRSA cage-associated infections was achieved with fosfomycin in combination with rifampin (83%). Fosfomycin may be used in combination with rifampin against MRSA implant-associated infections, but it cannot replace rifampin as an antibiofilm agent.

Background: Misconceptions and errors in the management of periprosthetic joint infection (PJI) can compromise the treatment success. The goal of this paper is to systematically describe twenty common mistakes in the diagnosis and management of PJI, to help surgeons avoid these pitfalls.Materials and methods: Common diagnostic and treatment errors are described, analyzed and interpreted.Results: Diagnostic errors include the use of serum inflammatory biomarkers (such as C-reactive protein) to rule out PJI, incomplete evaluation of joint aspirate, and suboptimal microbiological procedures (such as using swabs or collection of insufficient number of periprosthetic samples). Further errors are missing possible sources of distant infection in hematogenous PJI or overreliance on suboptimal diagnostic criteria which can hinder or delay the diagnosis of PJI or mislabel infections as aseptic failure. Insufficient surgical treatment or inadequate antibiotic treatment are further reasons for treatment failure and emergence of antimicrobial resistance. Finally, wrong surgical indication, both underdebridement and overdebridement or failure to individualize treatment can jeopardize surgical results.Conclusion: Multidisciplinary teamwork with infectious disease specialists and microbiologists in collaboration with orthopedic surgeons have a synergistic effect on the management of PJI. An awareness of the possible pitfalls can improve diagnosis and treatment results.