Culture-negative periprosthetic joint infections

Does Body Mass Index Affect the Success of Two-Stage Management of Periprosthetic Joint Infection?

INTRODUCTION

Obesity is associated with increased infection risk after primary total joint arthroplasty. In this retrospective cohort analysis, we sought to assess the association between body mass index (BMI) and infection recurrence after two-stage revision total joint arthroplasty (TJA) for periprosthetic joint infection (PJI).

METHODS

Patients were grouped by BMI (< 30, 30 to 40, and ≥ 40) as non-obese, obese, and morbidly obese, and assessed for associations and timing of PJI reinfection as well as readmissions and complications.

RESULTS

Following the two-stage revision, PJI reinfections increased from 11.5% in non-obese to 19.0% in obese and 25.9% in morbidly obese patients (P = 0.011). As BMI increased across the three groups, 90-day readmission rates following two-stage PJI revision significantly increased (8.6, 19.7, and 16.7%, respectively (P = 0.042)). The average time to reinfection decreased with obesity tercile (restricted-mean times of 4.5, 4.2, and 3.8 years with non-obese, obese, and morbidly obese, respectively (P = 0.023)).

DISCUSSION

The success of PJI management with two-stage arthroplasty is significantly impacted by patient BMI, with morbidly obese subjects having the worst outcomes. Attempts to modify BMI before completion of two-stage PJI treatment should be considered in the morbidly obese given high rates of recurrence.

Antimicrobial susceptibility testing of bone and joint pathogens using isothermal microcalorimetry

The rise in osteomyelitis and periprosthetic joint infections, in combination with increasing life expectancy and the prevalence of diabetes, underscores the urgent need for rapid and accurate diagnostic tools. Conventional culture-based methods are often time-consuming and prone to false-negatives, leading to prolonged and inappropriate antibiotic treatments. This study aims to improve osteomyelitis diagnostics by decreasing the time to detection and the time to an antibiotic susceptibility result to enable a targeted treatment using isothermal microcalorimetry (IMC). IMC measures heat flow in real-time, providing insights into bacterial metabolism without the need for labeling. Using clinical isolates from bone infections, assessing their response to antibiotics through IMC, we demonstrated that IMC could detect bacteria within 4 h and determine antimicrobial susceptibility profiles within 2-22 h (median 4.85, range 1.28-21.78). This is significantly faster than traditional methods. A decision tree, based on antibiotic susceptibility, accurately categorized pathogens, achieving high accuracy (74-100%), sensitivity (100%), and specificity (65-100%). These findings suggest that IMC could redefine diagnostics of bone and joint infections and potentially infections in general, offering timely and precise treatment guidance, thereby improving patient outcomes and reducing health care burdens. Further optimization and clinical validation are needed to fully integrate IMC into routine diagnostics.

The Role of Next-Generation Sequencing (NGS) in the Relationship between the Intestinal Microbiome and Periprosthetic Joint Infections: A Perspective

Periprosthetic joint infections are still a challenge in orthopedics and traumatology. Nowadays, genomics comes to the aid of diagnosis and treatment, in addition to traditional methods. Recently, a key role of the intestinal microbiota has been postulated, and great efforts are aimed at discovering its interconnection, which shows to be at different levels. Firstly, the gut microbiome influences the immune system through the gut-associated lymphoid tissue (GALT). A balanced microbiome promotes a strong immune response, which is essential to prevent all local and systemic infections, including PJI. Thus, a dysbiosis, i.e., the disruption of this system, leads to an imbalance between the various strains of microorganisms co-existing in the gut microbiome, which can result in a weakened immune system, increasing susceptibility to infections, including PJI. Additionally, the dysbiosis can result in the production of pro-inflammatory mediators that enter the systemic circulation, creating a state of chronic inflammation that can compromise the immune system's ability to fend off infections. Furthermore, the microbiome maintains the integrity of the gut barrier, preventing the translocation of harmful bacteria and endotoxins into the bloodstream; dysbiosis can compromise this protective "wall". In addition, the gut microbiome may harbor antibiotic-resistance genes; during antibiotic treatment for other infections or prophylaxis, these genes may be transferred to pathogenic bacteria, making the treatment of PJI more difficult. In this complex landscape, next-generation sequencing (NGS) technology can play a key role; indeed, it has revolutionized the study of the microbiome, allowing for detailed and comprehensive analysis of microbial communities. It offers insights into the functional potential and metabolic capabilities of the microbiome, studies the collective genome of the microbiome directly from environmental samples sequencing DNA without isolating individual organisms, analyzes the RNA transcripts to understand gene expression and functional activity of the microbiome, analyzes the RNA transcripts to understand gene expression and functional activity of the microbiome, investigates the metabolites produced by the microbiome and studies the entire set of proteins produced by the microbiome. NGS technology, the study of the micromyoma and its implications in the field of orthopedic trauma are innovative topics on which few publications are yet to be found in the international scientific literature. The costs are still high, the focus of research is maximum, and it will certainly change our approach to infections. Our study is an up-to-date review of the hot topic application of NGS in the study and investigation of periprosthetic infections and the microbiome.

Debridement, antibiotics and implant retention (DAIR) following hip and knee arthroplasty: results and findings of a multidisciplinary approach from a non-specialist prosthetic infection centre

INTRODUCTION

Prosthetic joint infection (PJI) is a catastrophic complication following arthroplasty surgery. Recently a debridement, antibiotics and implant retention (DAIR) procedure has gained popularity for PJI where a thorough debridement, irrigation and modular component exchange is undertaken.

METHOD

We present the outcome for DAIR, data collected prospectively, in a busy orthopaedic unit but not one specialising in PJI. All patients with PJI were included without loss of data or patients from 2012 to 2018 with a minimum follow-up of 5 years.

RESULTS

Four total knee replacements, 17 total hip replacements, one revision total hip replacement and three hip hemiarthroplasties are included with an average duration from onset of symptoms to the DAIR procedure of 11 days (range 1-22 days). Staphylococcus aureus (24%) and Staphylococcus epidermidis (32%) were the most common causative organisms, and the most common antibiotic regimens included intravenous teicoplanin and flucloxacillin. Average follow-up was 67 months (range 9-104 months). Only four patients went on to require revision surgery. An analysis of midterm patient outcome measures for 6 of the total hip replacement (THR) DAIR patients were compared with a database of 792 THRs (with a minimum two-year follow-up) carried out by the same surgeon revealed no significant difference in Oxford hip scores at one-year post-surgery (OHS DAIR 36.2 vs 39 for control group).

CONCLUSION

This study includes 25 consecutive patients treated with DAIR with only one reinfection, with a mean follow-up period of 5 years. Using a strict protocol, DAIR appears to offer a successful treatment strategy for the management of early PJI.

Future directions for early detection of fracture related infections

Introduction

Fracture related infection (FRI) refers to pathogens infecting a fracture site and hence impeding fracture healing. It is a significant complication that carries substantial disease burden and socio-economic costs, but has had limited scientific development. Hence, this paper will review the existing strategies for early detection of FRI, in the form of serum markers, molecular diagnostics and imaging modalities, and further discuss potential future directions for improved detection of FRI.

Existing Strategies for Diagnosis of FRI

The Anti-infection Global Expert Committee (AIGEC) developed a consensus definition for FRI in 2017, which includes confirmatory and suggestive criteria for diagnosis of FRI. Existing strategies for diagnosis include clinical, laboratory, histopathological, microbiological and radiological investigations.

Future Directions for Early Detection of FRI

With increasing recognition of FRI, early detection is crucial for early treatment to be enforced. We have identified potential areas for future development in diagnostics for early detection of FRI, which are discussed in this manuscript. They include inflammatory cytokines, serum calcium levels, platelet count, improved management of histopathological and microbiological specimens, metagenomics, wound biomarkers, gut microbiota analysis, and novel imaging technologies.

Immunohistochemistry Study of Antimicrobial Peptides as a Future Diagnostic and Prognostic Tool for Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) is a reputable complication of arthroplasty surgery. Septic loosening is an implant biofilm-related infection with different characteristics and treatment than aseptic loosening. Misdiagnosing PJI results in choosing an inappropriate treatment and, in most cases, failure to achieve asepsis. The worldwide increase of arthroplasty surgeries forces us to research more accurate ways to detect PJIs earlier, cheaper, and faster. In the current study, we investigated 52 arthroplasty revision surgeries (septic and aseptic) and, using immunohistochemistry staining of periprosthetic tissue, successfully demonstrated an important increase in antimicrobial peptides human β defensin-3 (HBD-3) and cathelicidin (LL-37) in the PJI group. Furthermore, we observed that patients with a positive LL-37 stain were associated with a more reserved prognosis at one-year follow-up. These promising results suggest that antimicrobial peptides HBD-3 and LL-37 could be used as future biomarkers for PJI detection.

Performance characteristics of genus or species-specific Polymerase Chain Reaction (PCR) for the microbial diagnosis of joint infections: A systematic review and meta-analysis

Joint infections cause significant morbidity and mortality. Rapid diagnosis enables prompt initiation of appropriate antimicrobial therapy and surgical treatment. We conducted a systematic review and meta-analysis to evaluate the accuracy of genus- or species-specific polymerase chain reaction (PCR) in diagnosing joint infections. The literature databases were searched for articles from January 2010 to December 2022. The meta-analysis using the split component synthesis (SCS) method, included 20 studies with 2,457 adult participants. The pooled sensitivity, specificity, diagnostic odds ratio, and AUC of PCR were 49 % (95 % CI [37.9-60.2]), 95.7 % (95 % CI [91.6-97.8]), 21.32, and 0.82 respectively. Sensitivity was highest for sonicate fluid and lowest for periprosthetic tissue. The mean turnaround time to results was 4.7 hours (SD 1.1). PCR is a favourable option for diagnosing joint infections due to its rapid results, but it has low sensitivity. To enhance diagnostic yield, the test should be used in conjunction with other methods.

Modern Microbiological Methods to Detect Biofilm Formation in Orthopedy and Suggestions for Antibiotic Therapy, with Particular Emphasis on Prosthetic Joint Infection (PJI)

Biofilm formation is a serious problem that relatively often causes complications in orthopedic surgery. Biofilm-forming pathogens invade implanted foreign bodies and surrounding tissues. Such a condition, if not limited at the appropriate time, often requires reoperation. This can be partially prevented by selecting an appropriate prosthesis material that prevents the development of biofilm. There are many modern techniques available to detect the formed biofilm. By applying them we can identify and visualize biofilm-forming microorganisms. The most common etiological factors associated with biofilms in orthopedics are: Staphylococcus aureus, coagulase-negative Staphylococci (CoNS), and Enterococcus spp., whereas Gram-negative bacilli and Candida spp. also deserve attention. It seems crucial, for therapeutic success, to eradicate the microorganisms able to form biofilm after the implantation of endoprostheses. Planning the effective targeted antimicrobial treatment of postoperative infections requires accurate identification of the microorganism responsible for the complications of the procedure. The modern microbiological testing techniques described in this article show the diagnostic options that can be followed to enable the implementation of effective treatment.

Sonication protocols and their contributions to the microbiological diagnosis of implant-associated infections: a review of the current scenario

Addressing the existing problem in the microbiological diagnosis of infections associated with implants and the current debate about the real power of precision of sonicated fluid culture (SFC), the objective of this review is to describe the methodology and analyze and compare the results obtained in current studies on the subject. Furthermore, the present study also discusses and suggests the best parameters for performing sonication. A search was carried out for recent studies in the literature (2019-2023) that addressed this research topic. As a result, different sonication protocols were adopted in the studies analyzed, as expected, and consequently, there was significant variability between the results obtained regarding the sensitivity and specificity of the technique in relation to the traditional culture method (periprosthetic tissue culture - PTC). Coagulase-negative Staphylococcus (CoNS) and Staphylococcus aureus were identified as the main etiological agents by SFC and PTC, with SFC being important for the identification of pathogens of low virulence that are difficult to detect. Compared to chemical biofilm displacement methods, EDTA and DTT, SFC also produced variable results. In this context, this review provided an overview of the most current scenarios on the topic and theoretical support to improve sonication performance, especially with regard to sensitivity and specificity, by scoring the best parameters from various aspects, including sample collection, storage conditions, cultivation methods, microorganism identification techniques (both phenotypic and molecular) and the cutoff point for colony forming unit (CFU) counts. This study demonstrated the need for standardization of the technique and provided a theoretical basis for a sonication protocol that aims to achieve the highest levels of sensitivity and specificity for the reliable microbiological diagnosis of infections associated with implants and prosthetic devices, such as prosthetic joint infections (PJIs). However, practical application and additional complementary studies are still needed.

Culture-negative periprosthetic joint infections: Do we have an issue?

Culture-negative periprosthetic joint infection (PJI) poses a significant challenge in clinical settings. The lack of information on causative organism(s) leads to uncertainties regarding the choice of antimicrobial treatment, which can potentially adversely influence the outcome. Recent advances in molecular-based diagnostic methods have the potential to address the difficulties associated with culture-negative PJIs. These technologies offer a solution to the existing clinical dilemma by providing identification of pathogens and guiding appropriate antimicrobial treatment. In this narrative review, we provide information regarding: 1) incidence and risk factors for culture-negative PJI; 2) the optimal antimicrobial therapy and duration of treatment for culture-negative PJI; 3) outcome comparison between culture-positive and culture-negative PJI; and 4) utilization of novel molecular diagnostic methods in culture-negative PJI, including pathogen identification, and the implementation of an antibiotic stewardship program.

Current Concepts on the Clinical and Economic Impact of Periprosthetic Joint Infections

Total joint arthroplasty (TJA) is a common procedure performed throughout the entire world in hopes of alleviating debilitating hip or knee pain. The projected number of TJAs performed in the United States alone is projected to exceed 1.9 million by 2030 and 5 million by 2040. With the significant increase in TJA performed, more periprosthetic joint infections (PJIs) are likely to be encountered. PJIs are a devastating complication of TJA. The economic and clinical burden must be understood and respected to minimize occurrence and allow optimal patient outcomes.

Risk factors for early septic failure after two-stage exchange total knee arthroplasty for treatment of periprosthetic joint infection

BACKGROUND

The cause of early septic failure after two-stage exchange revision total knee arthroplasty (TKA) for chronic periprosthetic joint infection (PJI) and the factors affecting it are not well known. The purpose of this study was to determine the surgical outcomes and the risk factors for early septic failure after two-stage revision TKA for chronic PJI.

METHODS

We identified a total of 246 adult patients who met the Musculoskeletal Infection Society (MSIS) diagnostic criteria for chronic PJI at two academic tertiary hospitals from March 2012 to December 2018. Finally, 151 patients who consecutively received two-stage exchange revision TKA for chronic PJI and who had a minimum 3-year follow-up were enrolled and retrospectively reviewed. Successful surgical treatment was evaluated for two-stage revision TKA and risk factors for early septic failure were identified.

RESULTS

Early septic failures occurred within 3 years after reimplantation in 48 patients (31.8%). After accounting for potentially confounding variables, we found that male patient [odds ratio (OR): 2.753, 95% confidence interval (CI) 1.099-6.893, p = 0.031], fungus or mycobacterial infection (OR: 5.224, 95% CI 1.481-18.433, p = 0.01), and positive culture at reimplantation (OR: 4.407, 95% CI 1.255-15.480, p = 0.021) were independently associated with early septic failure after two-stage exchange revision TKA.

CONCLUSION

Male patients, fungus or mycobacterial infection, and positive culture at reimplantation were independently associated with an increased risk of early septic failure after two-stage exchange revision TKA despite normal C-reactive protein values prior to reimplantation. Further prospective and high-quality studies are needed to determine the risk factors of two-stage exchange revision TKA for chronic PJI.

LEVEL OF EVIDENCE

level IV; retrospective comparison; treatment study.

Accuracy of Serological Markers, Synovial Fluid, Microbiological Culture, and Histopathological Examination for Diagnosing Periprosthetic Knee Infection

Objective  This study assessed the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of serological tests, synovial fluid markers, microbiological tissue culture, and histopathological examination of the periprosthetic membrane in diagnosing periprosthetic knee infection. Methods  This study is prospective, and it includes patients undergoing total knee arthroplasty revision surgery from November 2019 to December 2021. The analysis consisted of serological tests (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], and D-dimer), synovial fluid markers (leukocyte and polymorphonuclear cell counts), periprosthetic tissue culture, and histopathological examination of the periprosthetic membrane of all patients. Results  Sixty-two patients had periprosthetic joint infection (PJI) according to the 2018 International Consensus Meeting criteria (infection group), while 22 subjects had no infection. ESR sensitivity and specificity were 83.6% and 45.4%, respectively. CRP sensitivity and specificity were 64.5% and 100%, whereas D-dimer sensitivity and specificity were 78.9% and 25%, respectively. Leukocyte count sensitivity and specificity were 75.6% and 100%, polymorphonuclear cell count sensitivity and specificity were 33% and 100%, respectively. Periprosthetic tissue culture sensitivity and specificity culture were, respectively, 77.4% and 100%. Histopathological examination sensitivity and specificity were 43.7% and 100%, respectively. Conclusions  In our study, the total blood cell count in synovial fluid and microbiological cultures of periprosthetic tissues were the most accurate tests for PJI diagnosis. In contrast, polymorphonuclear cell percentage was the least accurate test for PJI diagnosis.

Development of droplet digital PCR-based detection of bacterial pathogens in prosthetic joint infection: a preliminary study using a synthesized model plasmid

Periprosthetic joint infection (PJI) can be diagnosed to characterize the microorganisms constituting a biofilm, which is an essential procedure for proper treatment. The gold standard method for detecting and identifying the causative microorganism is culture of microorganisms from patients-derived sample.; however, this method takes a long time and has low sensitivity. To compensate for these limitations, identification methods based on real-time PCR (RT-PCR) have been widely used. However, RT-PCR also has limitations, including low sensitivity and the requirement of a standard curve for quantification. Therefore, to prevent significant proliferation of pathogenic bacteria, it is important to detect a limited number of infectious bacteria during early stages of PJI. In the present study, we developed droplet digital PCR-based detection of bacterial pathogens in PJI. And we evaluated the analytical performance of the assay using a model plasmid, based on the 16S ribosomal DNA sequence of target bacteria commonly found in PJI. We also prepared genomic DNA extracted from E. coli, S. aureus, and S. epidermidis to test whether ddPCR provides better sensitivity and quantification of the target sequences. ddPCR detected 400 attograms of target DNA, which was more than 10 times less than that detected by real-time PCR using synthesized plasmid. In addition, ddPCR detected target regions from genomic DNA of 50 femtograms for E. coli, 70 femtograms for S. epidermidis, and 90 femtograms for S. aureus. The results indicate that ddPCR has the potential to decrease the microbial detection limit and provide precise detection, signifying its effectiveness for early PJI.

Multicenter evaluation of BioFire JI panel related to improved microbiological diagnostics on acute osteoarticular infections

Microbiological diagnosis of osteoarticular infections (OI) is crucial for a successful treatment. A prospective multicenter study including 262 synovial fluids with suspicion of acute OI was performed between July 2021 and October of 2022. BioFire Joint Infection Panel multiplex-PCR test was performed and results were compared with conventional cultures of synovial fluid specimens. In total, 136 microorganisms were detected, and fourteen samples were positive for more than one microorganism. In monomicrobial infections (n = 87) agreement with culture was 69%. In 26 samples, the multiplex PCR yield an additional positive result when culture result was negative. It helped in the detection of fastidious microorganisms as K. kingae and N. gonorrhoeae. This multiplex PCR has proven to be a useful technique that can be used for patients with high suspicion of acute OI in a rapid and automated manner.

Trends in Revision Knee Arthroplasty for Prosthetic Joint Infection: A Single-Center Study of 384 Knees at a High-Volume Center Between 2008 and 2021

BACKGROUND

Prosthetic joint infection (PJI) is one of the most devastating complications after total knee arthroplasty (TKA), and comorbidities increase the risk. We examined whether a temporal change has occurred in the demographics, especially regarding comorbidities, of patients who have PJI and were treated at our institution over a 13-year study period. In addition, we assessed the surgical methods used and the microbiology of the PJIs.

METHODS

Revisions (n = 384, 377 patients) due to PJI of the knee performed at our institution between 2008 and September 2021 were identified. All included PJIs fulfilled the 2013 International Consensus Meeting diagnostic criteria. The surgeries were categorized into one of the following categories: debridement, antibiotics, and retention (DAIR), 1-stage revision, and 2-stage revision. Infections were classified as early, acute hematogenous, and chronic.

RESULTS

No changes in the median age of the patients nor comorbidity burden were observed during the study period. However, the proportion of 2-stage revisions decreased remarkably from 57.6% in 2008 to 2009 to 6.3% in 2020 to 2021. A DAIR was the most used treatment strategy, but the proportion of 1-stage revisions increased the most. In 2008 to 2009, 12.1% of the revisions were 1-stage, but in 2020 to 2021, the proportion was 43.8%. The most common pathogen was Staphylococcus aureus (27.8%).

CONCLUSION

The comorbidity burden remained at the same level with no trends. A DAIR was the most used strategy, but the proportion of 1-stage revisions rose to almost the same level. The incidence of PJI varied between the years, but remained relatively low.

Diagnostic Value of Synovial Fluid Biomarkers for Periprosthetic Joint Infection: A Prospective, Double-blind Trial

BACKGROUND This prospective, double-blind study investigated the clinical diagnostic value of synovial fluid S100 calcium-binding protein A8 (S100A8) and S100 calcium-binding protein A9 (S100A9) in periprosthetic joint infection (PJI) and investigated the subtypes of a-defensin that have diagnostic value for PJI. MATERIAL AND METHODS Synovial fluid samples were collected from 82 patients with suspected PJI after total joint arthroplasty. Patients were divided into a PJI group (n=39) and non-PJI group (n=43). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to determine S100A8, S100A9, alpha-defensin, and internal reference standards in synovial fluid. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficiency of S100A8, S100A9, and alpha-defensin for PJI, as well as the diagnostic value in combination with common biomarkers of infection. RESULTS S100A8, 3 variants of S100A9, and 3 alpha-defensins (human neutrophil peptides [HNP]1-3) in synovial fluid were significantly higher in the PJI group than in the non-PJI group (P<0.001). The sensitivity, specificity, and the area under ROC curve (AUC) for diagnosing PJI were 97.4%, 86.0%, and 0.964 (95% CI: 0.929-0.998), respectively, for synovial fluid S100A8; 87.2%, 88.4% and 0.902 (95% CI: 0.823-0.980), respectively, for S100A9; and 89.7%, 83.7%, and 0.933 (95% CI: 0.884-0.982), respectively, for HNP1-3. The diagnostic efficiency was improved when combined with synovial fluid white blood cell count and percentage of polymorphonuclear neutrophils. CONCLUSIONS Synovial fluid S100A8, S100A9, and HNP1-3 have satisfactory diagnostic efficiency for the diagnosis of PJI, which will help clinicians to accurately diagnose PJI.

The Clinical Impact of Metagenomic Next-Generation Sequencing for the Diagnosis of Periprosthetic Joint Infection

Background

Synovial fluid metagenomic next-generation sequencing was introduced into the diagnosis of periprosthetic joint infection (PJI) in recent years. However, the clinical impact of mNGS remains unknown. Therefore, we performed a prospective cohort study to evaluate the clinical impact of mNGS for PJI diagnosis.

Materials and Methods

Between April 2019 and April 2021, a total of 201 patients with suspected PJI were recruited in a high-volume PJI revision center. All patients underwent joint aspiration before surgeries and the obtained synovial fluids were sent to tests for the diagnosis of PJI. Based on the clinical evaluation of these patients, the patients were categorized into three groups: Group A: the mNGS reports were not acted upon. Group B: mNGS confirmed the standard diagnostic tests of PJI and generated identical clinical impact compared to standard diagnostic tests. Group C: mNGS results guided clinical therapy. Then, the concordance between synovial mNGS and cultures was analyzed. After that, multivariate regressions were performed to explore the "targeted populations" of mNGS tests.

Results

A total of 107 patients were diagnosed with PJI based on the 2014 MSIS criteria and there were 33, 123, 45 patients in the group A, B, C respectively. The predictive factors of mNGS inducing clinical impact compared to standard diagnostic tests were negative culture results (adjusted OR: 5.88), previous history of joint infection (adjusted OR: 5.97), polymicrobial PJI revealed by culture (adjusted OR: 4.39) and PJI identified by MSIS criteria (adjusted OR: 17.06).

Conclusion

When standard diagnostic tests for PJI were performed, about 22% of synovial fluid mNGS tests can change the treatment protocols built on standard diagnostic tests and affect the clinical practice. Thus, the use of synovial fluid mNGS in some "target" populations is more valuable compared to others such as patients with previous joint infection, polymicrobial PJI, and culture-negative PJI.

Evidence Level

Level I.

Performance and Hypothetical Impact on Joint Infection Management of the BioFire Joint Infection Panel: a Retrospective Analysis

Pathogen identification is key in septic arthritis. Culture-based techniques are challenging, especially when patients have been pretreated with antibiotics or when difficult-to-culture bacteria are encountered. The BioFire joint infection assay (BJA) is a multiplex PCR panel which detects 31 of the most prevalent bacterial and fungal pathogens causing septic arthritis. Here, 123 cryoconserved contemporary synovial fluid samples from 120 patients underwent BJA analysis. Results were compared to those of culture-based diagnostics (standard of care [SOC]). Clinical data were collected, and the possible impact of the molecular diagnostic application on patient management was evaluated. Fifteen of 123 synovial fluid cultures grew bacterial pathogens. All on-panel pathogens (9/15) were correctly identified by the BJA. The BJA identified four additional bacterial pathogens in four SOC-negative cases. BJA sensitivity and specificity were 100% (95% confidence interval [CI], 69.2% to 100%) and 100% (95% CI, 96.8% to 100%), respectively. Compared to the SOC, the BJA would have resulted in faster provision of species identification and molecular susceptibility data by 49 h and 99 h, respectively. Clinical data analysis indicates that in BJA-positive cases, faster species ID could have led to timelier optimization of antibiotic therapy. This retrospective study demonstrates high sensitivity and specificity of the BJA to detect on-panel organisms in bacterial arthritis. The usefulness of the BJA in prosthetic-joint infections is limited, as important pathogens (i.e., coagulase negative staphylococci and Cutibacterium acnes) are not covered. Evidence from patient data analysis suggests that the assay might prove valuable for optimizing patient management in acute arthritis related to fastidious organisms or for patients who received antibiotics prior to specimen collection.

Prosthetic joint infection caused by an atypical gram-negative bacilli: Odoribactersplanchnicus

Prosthetic joint infection (PJI) is a devastating complication after total hip arthroplasty. Its management consists of both: a radical debridement and implant retention or exchange (depending on the timing of symptoms) and directed antibiotic therapy. Thus, the isolation of atypical microorganisms implies a challenge, where anaerobes are responsible for only 4% of cases. However, Odoribacter splanchnicus has not been reported as a cause of PJI yet. We present an 82 year-old woman who was diagnosed with hip PJI. A radical debridement, prosthetic withdrawal, and spacer introduction was performed. Despite the directed antibiotic therapy against E. coli which was first isolated, the patient persisted clinically febrile. An anaerobic Gram-negative rod was isolated and finally, Odoribacter splanchnicus was identified and confirmed by 16S rRNA gene sequencing. Then, antibiotic bitherapy with ciprofloxacin and metronidazole was started until 6 weeks after surgery. The patient had no signs of infection recurrence after then. This case report also shows the importance of genomic identification of rare microorganisms causing PJI, and also allows setting a directed antibiotic therapy which is crucial for infection eradication.

Pharmacokinetic and pharmacodynamic considerations for optimizing antimicrobial therapy used to treat bone and joint infections: an evidence-based algorithmic approach

INTRODUCTION

Bone and joint infections (BJIs) are a major health concern causing remarkable morbidity and mortality. However, which antimicrobial treatment could be the best according to specific clinical scenarios and/or to the pharmacokinetic/pharmacodynamic (PK/PD) features remains an unmet clinical need. This multidisciplinary opinion article aims to develop evidence-based algorithms for empirical and targeted antibiotic therapy of patients affected by BJIs.

AREAS COVERED

A multidisciplinary team of four experts had several rounds of assessment for developing algorithms devoted to empirical and targeted antimicrobial therapy of BJIs. A literature search was performed on PubMed-MEDLINE (until April 2023) to provide evidence for supporting therapeutic choices. Four different clinical scenarios were structured according to specific infection types (i.e. vertebral osteomyelitis, prosthetic joint infections, infected non-unions and other chronic osteomyelitis, and infectious arthritis), need or not of surgical intervention or revision, isolation or not of clinically relevant bacterial pathogens from blood and/or tissue cultures, and PK/PD features of antibiotics.

EXPERT OPINION

The proposed therapeutic algorithms were based on a multifaceted approach considering the peculiar features of each antibiotic (spectrum of activity, PK/PD properties, bone penetration rate, and anti-biofilm activity), and could be hopefully helpful in improving clinical outcome of BJIs.

Microbiological Profile of Periprosthetic Knee Infections in a Brazilian Unified Health System Hospital Specialized in Highly Complex Orthopedic Surgeries

Objective  We studied the microbiological profile of periprosthetic knee infections treated in a Brazilian tertiary hospital. Methods  The study included all patients undergoing revision surgery for total knee arthroplasty (RTKA) between November 2019 and December 2021, with a diagnosis of periprosthetic infection confirmed per the 2018 International Consensus Meeting (ICM) criteria. Results  Sixty-two patients had a periprosthetic joint infection (PJI) per the 2018 ICM criteria. Cultures were monomicrobial in 79% and polymicrobial in 21% of cases. The most frequent bacterium in microbiological tissue and synovial fluid cultures was Staphylococcus aureus , observed in 26% of PJI patients. Periprosthetic joint infection with negative cultures occurred in 23% of patients. Conclusion  Our results show the following: i) a high prevalence of Staphylococcus as an etiological agent for knee PJI; ii) a high incidence of polymicrobial infections in early infections; iii) the occurrence of PJI with negative cultures in approximately one fourth of the subjects.

Clinical and Histological Features of Prosthetic Joint Infections May Differ in Patients With Inflammatory Arthritis and Osteoarthritis

Background: Patients with inflammatory arthritis are at increased risk of prosthetic joint infections (PJIs), but diagnosis in these patients can be challenging because active inflammatory arthritis produces elevated inflammatory markers that may mimic those seen in PJI. Purpose: In this pilot study, we sought to identify the clinical, microbiologic, and histopathologic features of culture-positive and culture-negative PJI in patients with inflammatory arthritis who underwent total hip arthroplasty (THA) or total knee arthroplasty (TKA). We also sought to obtain preliminary data to support a definitive study of optimal methods for PJI diagnosis in patients with inflammatory arthritis. Methods: We performed a retrospective analysis of TKA and THA patients treated for PJI from 2009 to 2018 at a single tertiary care orthopedic institution. Data were extracted from a longitudinally maintained hospital infection database. We reviewed hematoxylin and eosin slides of osteoarthritis and inflammatory arthritis PJI cases matched 3:1, respectively, by age, sex, and culture status. Clinical characteristics were evaluated using the Fisher exact test, χ² test, Student t test, and Mann-Whitney U test where appropriate. Results: A total of 807 PJI cases were identified (36 inflammatory arthritis and 771 osteoarthritis cases). Patients with inflammatory arthritis presented younger, had a higher Charlson Comorbidity Index, more frequently used glucocorticoids, were more likely women, and had a higher proportion of culture-negative PJI compared with osteoarthritis patients. Of the 88 inflammatory arthritis cases reviewed for histopathology, a higher proportion of culture-positive than culture-negative PJI cases had >10 polymorphonuclear leucocytes per high-power field and met Musculoskeletal Infection Society criteria but presented with less chronic inflammation. Conclusions: This retrospective prognostic study suggests that culture-negative PJI may be more frequent in patients with inflammatory arthritis than in those with osteoarthritis. Chronic infections, antibiotic use, or misdiagnosis may be contributing factors to unclear PJI diagnoses among culture-negative cases. This preliminary work supports the need for further studies to assess the differences in clinical features between culture-negative and culture-positive PJI in patients with inflammatory arthritis and the ability of biological diagnostic markers to discriminate between them in this population.

Metagenomic Next-Generation Sequencing for Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) after arthroplasty is a major complication, which requires significant resources, resulting in high costs for the medical system. In recent years, significant progress has been made in the diagnosis and treatment of periprosthetic infections, the identification of the pathogen being the central element in the establishment of targeted antibiotic therapy. Next-generation sequencing (NGS) or metagenomic NGS (mNGS) represents a promising, fast alternative, with increased specificity and sensitivity compared to identification methods using conventional culture media, thus enabling an increased rate of identification of pathogenic microorganisms and antibiotic resistance genes (ARG). The purpose of this article was to highlight new molecular diagnostic methods for periprosthetic joint infections and their involvement in treatment efficiency. NGS technologies are cutting-edge techniques that may challenge the PJI diagnostic model.

The Challenge of Emerging Resistant Gram-Positive Pathogens in Hip and Knee Periprosthetic Joint Infections

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An increase in resistant bacterial pathogens has occurred over the last 4 decades.

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Careful patient selection and improving or correcting risk factors for periprosthetic joint infection (PJI) before elective surgical treatment are strongly recommended.

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Appropriate microbiological methods, including those used to detect and grow Cutibacterium acnes, are recommended.

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Antimicrobial agents used in the prevention or management of infection should be selected appropriately and the duration of therapy should be carefully considered in order to mitigate the risk of developing bacterial resistance.

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Molecular methods including rapid polymerase chain reaction (PCR) diagnostics, 16S sequencing, and/or shotgun and/or targeted whole-genome sequencing are recommended in culture-negative cases of PJI.

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Expert consultation with an infectious diseases specialist (if available) is recommended to assist with the appropriate antimicrobial management and monitoring of patients with PJI.

Mapping bacterial biofilm on explanted orthopedic hardware: An analysis of 14 consecutive cases

Hardware implanted during primary total joint arthroplasty carries a serious risk for periprosthetic joint infection (PJI). The formation of bacterial biofilms, which are highly tolerant of antibiotics and host immunity, is recognized as being a major barrier to treatment. It is not known whether some components and their surface features are more prone to biofilm than others. This study attempted to map biofilm on different components and features of orthopedic hardware recovered during revision. Implant surface culture (ISC) was used on 53 components from 14 hip and knee revisions. ISC achieves a thin agar coating over components, followed by incubation and observation for colony outgrowth over 9 days. Recovered organisms were identified by selective culture and 16s rRNA sequencing. Outcomes were compared with clinical culturing and PJI diagnosis based on 2013 Musculoskeletal Infection Society criteria. ISC paralleled clinical culturing with a sensitivity of 100% and a specificity of 57.1%. When compared to Musculoskeletal Infection Society criteria, sensitivity remained at 100% while specificity was 80%. Biofilm accumulation was patchy and heterogeneous throughout different prostheses, though notably the non-articulating surfaces between the tibial tray and polyethylene insert showed consistent growth. On individual components, ridges and edges consistently harbored biofilm, while growth elsewhere was case dependent. ISC successfully identified microbial growth with high sensitivity while also revealing that biofilm growth was commonly localized to particular locations. Understanding where biofilm formation occurs most often on implanted hardware will help guide debridement, retention choices, and implant design.

Trends in Revision Hip Arthroplasty for Prosthetic Joint Infection: A Single-Center Study of 423 Hips at a High-Volume Center Between 2008 and 2021

BACKGROUND

Prosthetic joint infection (PJI) is one of the most devastating complications after total hip arthroplasty (THA), and comorbidities increase the risk. We examined whether there was a temporal change in the demographics, especially regarding comorbidities, of patients who have PJIs and were treated over a 13-year study period at a high-volume academic joint arthroplasty center. In addition, the surgical methods used and the microbiology of the PJIs were assessed.

METHODS

Revisions (n = 423, 418 patients) due to PJI of the hip performed at our institution between 2008 and September 2021 were identified. All included PJIs fulfilled the 2013 International Consensus Meeting diagnostic criteria. The surgeries were categorized into one of the following categories: debridement, antibiotics, and implant retention, 1-stage revision, and 2-stage revision. Infections were classified as early, acute hematogenous, and chronic infections.

RESULTS

There was no change in the median age of the patients, but the proportion of ASA-class 4 patients increased from 10.5% to 20%. The incidence of early infections increased from 0.11 per 100 primary THAs in 2008 to 1.09 in 2021. The incidence of 1-stage revisions increased the most, rising from 0.10 per 100 primary THAs in 2010 to 0.91 per 100 primary THAs in 2021. Furthermore, the proportion of infections caused by Staphylococcus aureus increased from 26.3% in 2008 to 2009 to 40% in 2020 to 2021.

CONCLUSION

The comorbidity burden of PJI patients increased during the study period. This increase may present a treatment challenge, as comorbidities are known to have a negative effect on PJI treatment outcomes.

A case of prosthetic joint infection caused by Mycobacterium tuberculosis complicated secondary bacterial infection after knee joint replacement surgery

Mycobacterium tuberculosis (M. tuberculosis) is a rare cause of prosthetic joint infection (PJI). Previous studies have reported that many cases of PJI caused by M. tuberculosis have no medical history of active tuberculosis (TB) or other localization, which contributes to diagnostic difficulties. Furthermore, owing to the limited number of studies on treatment, appropriate treatment strategies, such as the duration of anti-tuberculosis (anti-TB) drugs and surgical indications, remain unclear. We report a case of PJI caused by M. tuberculosis and secondary pyogenic arthritis caused by Staphylococcus aureus and Streptococcus dysgalactiae in a 67-year-old man after knee joint replacement surgery in Japan, which was a moderately endemic country until 2020 and a low endemic country since 2021. Although he had no past medical history or close contact with TB, he was diagnosed with PJI caused by M. tuberculosis, following the culture of a synovectomy specimen. He underwent two-stage surgery and was treated with anti-TB drugs for a total of 12 months and recovered without recurrence. Based on our case and previous studies, there are three points of clinical significance for PJI caused by M. tuberculosis. First, about one year of anti-TB drugs with two staged joint revision resulted in a good course of treatment. Second, surgical treatment might be considered in cases complicated by secondary bacterial infection. Third, because the diagnosis of PJI caused by M. tuberculosis is difficult, TB should be considered in the differential diagnosis of routine bacterial culture-negative PJI, especially in endemic areas.

Success of staged revision reverse total shoulder arthroplasty in eradication of periprosthetic joint infection

INTRODUCTION

Management of periprosthetic joint infection (PJI) in shoulder arthroplasty remains a challenge, with no established gold standard treatment. This study presents the unique experience of a high-volume single-surgeon, single-institution approach on staged revision reverse total shoulder arthroplasty (RTSA) for infection. The authors theorize that staged revision RTSA is an effective treatment for PJI.

MATERIALS AND METHODS

Between 2013 and 2018, 38 patients underwent a staged RTSA for treatment of PJI. Patient histories were collected and classified using Cierny-Mader classification. Infection workup for all patients included radiographs, laboratory indices, and computed tomographic aspiration arthrogram. PJI was identified based on high clinical and radiographic suspicion, elevated serologic markers, and/or aspirate culture results per 2018 International Consensus Meeting Shoulder guidelines on Orthopedic Infections. All patients underwent first stage with implant removal, irrigation and débridement, and antibiotic spacer placement. Next, intravenous antibiotics were administered by infectious disease consultants for a minimum of 6 weeks. Infection workup was then repeated and, if normalized, final-stage revision commenced with antibiotic spacer removal and revision to RTSA. If indices were persistently abnormal, an additional stage of débridement and spacer placement procedure was performed. Treatment failure was defined as recurrent periprosthetic infection after final prosthesis implantation or persistently elevated indices despite adequate débridement and spacer placement.

RESULTS

Mean age of the cohort was 68 (standard deviation [SD] 8.9) years and mean follow-up was 33 (SD 14) months with 34 Cierny-Mader C hosts and 4 B hosts. Patients underwent a mean of 2 (SD 1.1) previous surgeries. The staged revision protocol was successful in 34 (89.5%) patients for management of PJI. Four patients (10.5%) were considered failures with recurrent infections at a mean of 13 months (range 2-26 months) after the final RTSA implantation and underwent repeat staged revisions. Of the 34 patients who had successful infection eradication, 31 had 2-stage treatment and 3 had to undergo 3 stages. There were no treatment-associated mortalities and 10 major complications (26%), including permanent neuropathy, instability, and periprosthetic fractures. The most common cultured microorganism was Cutibacterium acnes (18%), with no polymicrobial infections detected.

DISCUSSION

Although there are multiple treatment options for PJI management, staged revision remains an effective means of treatment. Although there were several patients who required an additional stage of treatment, and a significant complication rate, staged revision RTSA proved successful in the ultimate eradication of the PJI.

Increased Incidence of Methicillin-Resistant Staphylococcus aureus in Knee and Hip Prosthetic Joint Infection

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication of knee and hip arthroplasty. Past literature has shown that gram-positive bacteria are commonly responsible for these infections, although limited research exists studying the changes in the microbial profile of PJIs over time. This study sought to analyze the incidence and trends of pathogens responsible for PJI over three decades.

METHODS

This is a multi-institutional retrospective review of patients who had a knee or hip PJI from 1990 to 2020. Patients with a known causative organism were included and those with insufficient culture sensitivity data were excluded. There were 731 eligible joint infections from 715 patients identified. Organisms were divided into multiple categories based on genus/species and 5-year increments were used to analyze the study period. The Cochran-Armitage trend tests were used to evaluate linear trends in microbial profile over time and a P-value <.05 was considered statistically significant.

RESULTS

There was a statistically significant positive linear trend in the incidence of methicillin-resistant Staphylococcus aureus over time (P = .0088) as well as a statistically significant negative linear trend in the incidence of coagulase-negative staphylococci over time (P = .0018). There was no statistical significance between organism and affected joint (knee/hip).

CONCLUSION

The incidence of methicillin-resistant Staphylococcus aureus PJI is increasing over time, whereas, coagulase-negative staphylococci PJI is decreasing, paralleling the global trend of antibiotic resistance. Identifying these trends may help with the prevention and treatment of PJI through methods such as remodeling perioperative protocols, modifying prophylactic/empiric antimicrobial approaches, or transitioning to alternative therapeutic strategies.

2022 American Association of Hip and Knee Surgeons Symposium: Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is the leading cause of failure in patients undergoing total joint arthroplasty. This article is a brief summary of a symposium on PJI that was presented at the annual AAHKS meeting. It will provide an overview of current technqiues in the prevention, diagnosis, and management of PJI. It will also highlight emerging technologies in this setting.

Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure

Arthroplasty failure is a major complication of joint replacement surgery. It can be caused by periprosthetic joint infection (PJI) or non-infectious etiologies, and often requires surgical intervention and (in select scenarios) resection and reimplantation of implanted devices. Fast and accurate diagnosis of PJI and non-infectious arthroplasty failure (NIAF) is critical to direct medical and surgical treatment; differentiation of PJI from NIAF may, however, be unclear in some cases. Traditional culture, nucleic acid amplification tests, metagenomic, and metatranscriptomic techniques for microbial detection have had success in differentiating the two entities, although microbiologically negative apparent PJI remains a challenge. Single host biomarkers or, alternatively, more advanced immune response profiling-based approaches may be applied to differentiate PJI from NIAF, overcoming limitations of microbial-based detection methods and possibly, especially with newer approaches, augmenting them. In this review, current approaches to arthroplasty failure diagnosis are briefly overviewed, followed by a review of host-based approaches for differentiation of PJI from NIAF, including exciting futuristic combinational multi-omics methodologies that may both detect pathogens and assess biological responses, illuminating causes of arthroplasty failure.

Application of next-generation sequencing technology in the detection of pathogenic bacteria of the periprosthetic joint infection after arthroplasty

To investigate the application value of next-generation sequencing (NGS) technology in the detection of pathogenic bacteria in the periprosthetic joint infection after arthroplasty. Twenty-two cases of patients with joint infection after arthroplasty in our hospital from March 2020 to March 2021 were selected, with 11 cases of knee and 11 cases of hip, including 8 cases of male and 14 cases of female, and an average age of 63.55 ± 13.11 years old (range from 28 to 85). Microbiological culture results of synovial fluid and periprosthetic joint tissue and NGS results of periprosthetic joint tissue were collected. The detection rate of NGS and microbiological culture were calculated and statistically analysed by paired χ² test. Among the 22 patients with joint infection after arthroplasty, the positive rate of NGS was 90.91% (20/22), whereas the positive rate of bacterial culture was 50.00% (11/22). Paired chi-square test showed a statistically significant difference in the detection rate between the two groups (P = .0029). In the detection of pathogenic microorganism, NGS detected 12 kinds of bacteria, Staphylococcus aureus in 3 patients, Staphylococcus epidermidis in 5 cases, Streptococcus 1 case, Streptococcus dysgalactiae 1 case, Xanthomonas campestris 3 cases, Escherichia coli 2 cases, Bacillus cereus 2 cases, Klebsiella pneumoniae 1 case, Finegoldia magna 1 case, Corynebacterium klopensteriella in 1 case, Brucella 1 case, and Aspergillus flavus 1 case. Bacterial culture detected 6 kinds of bacteria, included 5 cases of Staphylococcus epidermis (including 3 cases of Methicillin-resistant coagulase-negative Staphylococcus, (MRSCoN)), 2 cases of Staphylococcus aureus (both Methicillin-resistant Staphylococcus aureus, (MRSA)), 1 case of Klebsiella pneumoniae, 1 case of Staphylococcus hominis (MRSCoN), 1 case of G⁺ bacillus, and 1 case of Brucella. Compared with bacterial culture, NGS technology has some advantages in the detection efficiency, detection rate, and comprehensiveness, which might be greater diagnostic value in the joint fluid of infection after arthroplasty.

Diagnostic Performance of Metagenomic Next⁃Generation Sequencing in the Diagnosis of Prosthetic Joint Infection Using Tissue Specimens

Purpose

The purpose of this study was to evaluate the ability of metagenomic next-generation sequencing (mNGS) diagnosing prosthetic joint infection (PJI) using tissue from hip/knee rapidly and precisely, especially in patients who had received antibiotic treatment within the preceding two weeks.

Methods

From May 2020 to March 2022, 52 cases with suspected PJI were enrolled. mNGS was performed on surgical tissue samples. The sensitivity and specificity of mNGS in diagnosis was evaluated using culture in conjunction with MSIS criteria. This study also looked at how antibiotic use affected culture and mNGS efficacy.

Results

According to MSIS criteria, 31 of the 44 cases had PJI, and 13 were classified in the aseptic loosening group. Sensitivity, specificity, positive/negative predictive value (PPV/NPV), positive/negative likelihood ratio (PLR/NLR), and area under the curve (AUC) of mNGS assay were 80.6% (71.9-91.8%), 84.6 (73.7-97.9%), 92.6 (84.2-98.7%), 64.7 (58.6-74.7%), 5.241 (4.081-6.693), 0.229 (0.108-0.482) and 0.826 (0.786-0.967), respectively, with MSIS as a reference. When MSIS was used as a reference, the results of culture assay were 45.2% (40.8-51.5%), 100 (100.0-100.0%), 100 (100.0-100.0%), 43.3 (39.1-49.5%), +∞, 0.548 (0.396-0.617) and 0.726 (0.621-0.864), respectively. The AUC values for mNGS and culture were 0.826 and 0.731, respectively, and the differences were insignificant. mNGS demonstrated higher sensitivity than culture in PJI subjects who had previously received antibiotic treatment within 2 weeks (69.5% vs 23.1%, P = 0.03).

Conclusion

In our series, mNGS yield a higher sensitivity for diagnosis and pathogen detection of PJI compared to microbiological culture. Additionally, mNGS is less affected by prior antibiotic exposure.

Decreased serum superoxide dismutase concentration has a high value for the diagnosis of periprosthetic joint infection-a single-center, retrospective study

PURPOSE

As the most serious complication of total knee arthroplasty (TKA), periprosthetic joint infection (PJI) often leads to disastrous consequences. An accurate preoperative diagnosis plays a significant role in saving prostheses and optimizing treatment outcomes. Through this retrospective case-control study, we aimed to investigate the potential of superoxide dismutase (SOD) as a novel serum biomarker in the diagnosis of PJI.

METHODS

We conducted a retrospective review of all patients who underwent TKA and received adequate follow-ups in our hospital from June 2015 to December 2021. A total of 50 patients were enrolled in the PJI group based on the 2018 International Consensus Meeting (ICM) criteria. Besides that, we enrolled 100 patients who underwent TKA in the same period and had a good postoperative course in the control group. Patient characteristics, comorbidities, laboratory results (serum, synovial, and microbial), and intraoperative findings (purulence and histopathology) were documented and compared by univariate analysis. Receiver operating characteristic (ROC) analysis was used to determine the sensitivity, specificity, and diagnostic performance.

RESULTS

The median serum SOD level in the PJI and control group was 135.95 ± 24.47 U/ml (IQR, 111.85-158.30 U/ml) and 173.83 ± 13.9 U/ml (IQR,162.83-183.5 U/ml) (p < 0.05), respectively. With the calculated cutoff of SOD at 149.5U/L, the area under the ROC curve (AUC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), were 0.919, 0.72, 0.97, 0.923, and 0.874, respectively. In subgroup analysis, the specificity of SOD in diagnosing culture-negative PJI remained extremely high (0.98). Combined diagnosis of serum SOD and C-reactive protein (CRP) made AUC increase to 0.972.

CONCLUSION

Serum SOD showed great potential in the diagnosis of PJI.

Imaging joint infections using D-methyl-11C-methionine PET/MRI: initial experience in humans

PURPOSE

Non-invasive imaging is a key clinical tool for detection and treatment monitoring of infections. Existing clinical imaging techniques are frequently unable to distinguish infection from tumors or sterile inflammation. This challenge is well-illustrated by prosthetic joint infections that often complicate joint replacements. D-methyl-11C-methionine (D-11C-Met) is a new bacteria-specific PET radiotracer, based on an amino acid D-enantiomer, that is rapidly incorporated into the bacterial cell wall. In this manuscript, we describe the biodistribution, radiation dosimetry, and initial human experience using D-11C-Met in patients with suspected prosthetic joint infections.

METHODS

614.5 ± 100.2 MBq of D-11C-Met was synthesized using an automated in-loop radiosynthesis method and administered to six healthy volunteers and five patients with suspected prosthetic joint infection, who were studied by PET/MRI. Time-activity curves were used to calculate residence times for each source organ. Absorbed doses to each organ and body effective doses were calculated using OLINDA/EXM 1.1 with both ICRP 60 and ICRP 103 tissue weighting factors. SUVmax and SUVpeak were calculated for volumes of interest (VOIs) in joints with suspected infection, the unaffected contralateral joint, blood pool, and soft tissue background. A two-tissue compartment model was used for kinetic modeling.

RESULTS

D-11C-Met was well tolerated in all subjects. The tracer showed clearance from both urinary (rapid) and hepatobiliary (slow) pathways as well as low effective doses. Moreover, minimal background was observed in both organs with resident micro-flora and target organs, such as the spine and musculoskeletal system. Additionally, D-11C-Met showed increased focal uptake in areas of suspected infection, demonstrated by a significantly higher SUVmax and SUVpeak calculated from VOIs of joints with suspected infections compared to the contralateral joints, blood pool, and background (P < 0.01). Furthermore, higher distribution volume and binding potential were observed in suspected infections compared to the unaffected joints.

CONCLUSION

D-11C-Met has a favorable radiation profile, minimal background uptake, and fast urinary extraction. Furthermore, D-11C-Met showed increased uptake in areas of suspected infection, making this a promising approach. Validation in larger clinical trials with a rigorous gold standard is still required.

Assessment of Predictors of Infection in Primary Knee and Hip Arthroplasty: A Case-control Study

Objective This study assesses risk factors for periprosthetic joint infection after elective primary total knee or hip arthroplasty. Methods  The study included 706 medical records of patients undergoing elective primary total hip or knee arthroplasty from January to December 2018. We used a multivariate analysis of infection predictors through a logistic regression model. The R software performed all statistical analysis. Results  The prevalence of infection in the sample was 2.0% (14 cases). Most patients were women (79.6%), with an afflicted right side (50.6%), and underwent a total knee arthroplasty (61.3%). Significant risk factors ( p  < 0.05) for infection included surgical time greater than 120 minutes ( p  = 0.009) and a history of diabetes ( p  = 0.025). Conclusion  The risk of infection after elective primary total knee or hip arthroplasty is higher when the surgical procedure is lengthy (over 120 minutes), or the patient has a history of diabetes mellitus. Level of Evidence  IIIB, retrospective, case-control study.

Validation of the diagnostic criteria of the consensus definition of fracture-related infection

BACKGROUND

The recently developed fracture-related infection (FRI) consensus definition, which is based on specific diagnostic criteria, has not been fully validated in clinical studies. We aimed to determine the diagnostic performance of the criteria of the FRI consensus definition and evaluated the effect of the combination of certain suggestive and confirmatory criteria on the diagnostic performance.

METHODS

A multicenter, multi-national, retrospective cohort study was performed. Patients were subdivided into an FRI or a control group, according to the treatment they received and the recommendations from a multidisciplinary team ('intention to treat'). Exclusion criteria were patients with an FRI diagnosed outside the study period, patients younger than 18 years of age, patients with pathological fractures or patients with fractures of the skull, cervical, thoracic and lumbar spine. Minimum follow up for all patients was 18 months.

RESULTS

Overall, 637 patients underwent revision surgery for suspicion of FRI. Of these, 480 patients were diagnosed with FRI, treated accordingly, and included in the FRI group. The other 157 patients were included in the control group. The presence of at least one confirmatory sign was associated with a sensitivity of 97.5%, a specificity of 100% and a high discriminatory value (AUROC 0.99, p < 0.001). The presence of a clinical confirmatory criterion or, if not present, at least one positive culture was associated with the highest diagnostic performance (sensitivity: 98.6%, specificity: 100%, AUROC: 0.99 (p < 0.001)). In the subgroup of patients without clinical confirmatory signs at presentation, specificities of at least 95% were found for the clinical suggestive signs of fever, wound drainage, local warmth and redness.

CONCLUSIONS

The presence of at least one confirmatory criterion identifies the vast majority of patients with an FRI and was associated with an excellent diagnostic discriminatory value. Therefore, our study validates the confirmatory criteria of the FRI consensus definition. Infection is highly likely in case of the presence of a single positive culture with a virulent pathogen. When certain clinical suggestive signs (e.g., wound drainage) are observed (individually or in combination and even without a confirmatory criterion), it is more likely than not, that an infection is present.

Retrospective Preliminary Assessment of Routine Follow-Up Low-Field Magnetic Resonance Imaging in Dogs Presumptively Diagnosed With Discospondylitis

Background

The usefulness of routine follow-up Magnetic Resonance Imaging (MRI-2) in asymptomatic dogs treated for discospondylitis is unknown.

Methods

This cross-sectional retrospective study investigated the features of MRI-2 in a heterogeneous group of dogs treated for discospondylitis, and if these were associated with the presence or absence of clinical signs. After comparing initial MRI (MRI-1) and MRI-2, an observer, blinded to the dog's clinical signs, described the MRI-2 findings. The study population was then divided into symptomatic or asymptomatic at the time of MRI-2. Two separate observers subjectively classified the discospondylitis as active or inactive. Repeatability and interobserver agreement were evaluated.

Results

A total of 25 dogs were included. At the time of MRI-2 16 (64%) dogs were asymptomatic and 9 (36%) were symptomatic. Based on MRI-2, 20 (80%) and 18 (72%) out of 25 dogs were considered to have active discospondylitis by the first and second observers, respectively. Interobserver agreement was moderate. No MRI-2 features were associated with the clinical status. The subjective classification of inactive discospondylitis was significantly associated with asymptomatic clinical status, but the classification of active discospondylitis was evenly distributed between groups.

Conclusion

This study did not identify a meaningful association between the clinical status of dogs treated for presumptive discospondylitis and MRI-2 results. There were no specific MRI-2 features which were associated with the clinical status.

Prosthetic joint infection of the hip and knee due to Mycobacterium species: A systematic review

BACKGROUND

Mycobacterium species (Mycobacterium sp) is an emerging cause of hip and knee prosthetic joint infection (PJI), and different species of this organism may be responsible for the same.

AIM

To evaluate the profile of hip and knee Mycobacterium PJI cases as published in the past 30 years.

METHODS

A literature search was performed in PubMed using the MeSH terms “Prosthesis joint infection” AND “Mycobacterium” for studies with publication dates from January 1, 1990, to May 30, 2021. To avoid missing any study, another search was performed with the terms “Arthroplasty infection” AND “Mycobacterium” in the same period as the previous search. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses chart was used to evaluate the included studies for further review. In total, 51 studies were included for further evaluation of the cases, type of pathogen, and treatment of PJI caused by Mycobacterium sp.

RESULTS

Seventeen identified Mycobacterium sp were reportedly responsible for hip/knee PJI in 115 hip/knee PJI cases, whereas in two cases there was no mention of any specific Mycobacterium sp. Mycobacterium tuberculosis (M. tuberculosis) was detected in 50/115 (43.3%) of the cases. Nontuberculous mycobacteria (NTM) included M. fortuitum (26/115, 22.6%), M. abscessus (10/115, 8.6%), M. chelonae (8/115, 6.9%), and M. bovis (8/115, 6.9%). Majority of the cases (82/114, 71.9%) had an onset of infection > 3 mo after the index surgery, while in 24.6% (28/114) the disease had an onset in ≤ 3 mo. Incidental intraoperative PJI diagnosis was made in 4 cases (3.5%). Overall, prosthesis removal was needed in 77.8% (84/108) of the cases to treat the infection. Overall infection rate was controlled in 88/102 (86.3%) patients with Mycobacterium PJI. Persistent infection occurred in 10/108 (9.8%) patients, while 4/108 (3.9%) patients died due to the infection.

CONCLUSION

At least 17 Mycobacterium sp can be responsible for hip/knee PJI. Although M. tuberculosis is the most common causal pathogen, NTM should be considered as an emerging cause of hip/knee PJI.

Serum and Synovial Markers in Patients with Rheumatoid Arthritis and Periprosthetic Joint Infection

Current diagnostic standards for PJI rely on inflammatory markers that are typically elevated in autoimmune diseases, thus making the diagnosis of PJI in patients with rheumatoid arthritis and joint replacement particularly complicated. There is a paucity of data on differentiating PJI from rheumatoid arthritis in patients with previous arthroplasty. In this study, we retrospectively analyzed the cases of 17 patients with rheumatoid arthritis and 121 patients without rheumatoid disease who underwent surgical intervention due to microbiology-positive PJI of the hip or knee joint. We assessed clinical patient characteristics, laboratory parameters, and prosthesis survival rates in patients with and without rheumatoid arthritis and acute or chronic PJI. ROC analysis was conducted for the analyzed parameters. In patients with chronic PJI, peripheral blood CRP (p = 0.05, AUC = 0.71), synovial WBC count (p = 0.02, AUC = 0.78), synovial monocyte cell count (p = 0.04, AUC = 0.75), and synovial PMN cell count (p = 0.02, AUC = 0.80) were significantly elevated in patients with rheumatoid arthritis showing acceptable to excellent discrimination. All analyzed parameters showed no significant differences and poor discrimination for patients with acute PJI. Median prosthesis survival time was significantly shorter in patients with rheumatoid arthritis (p = 0.05). In conclusion, routinely used laboratory markers have limited utility in distinguishing acute PJI in rheumatoid patients. In cases with suspected chronic PJI but low levels of serum CRP and synovial cell markers, physicians should consider the possibility of activated autoimmune arthritis.

Defining a Synovial Fluid White Blood Cell Count Threshold to Predict Periprosthetic Infection after Shoulder Arthroplasty

BACKGROUND

The diagnosis of periprosthetic shoulder infection (PSI) requires a thorough diagnostic workup. Synovial fluid aspiration has been proven to be a reliable tool in the diagnosis of joint infections of the lower extremity, but shoulder specific data is limited. This study defines a threshold for synovial fluid white blood cell count (WBC) and assesses the reliability of microbiological cultures.

METHODS

Retrospective study of preoperative and intraoperative fluid aspiration of 31 patients who underwent a revision of a shoulder arthroplasty (15 with PSI defined by IDSA criteria, 16 without infection). The threshold for WBC was calculated by ROC/AUC analysis.

RESULTS

WBC was significantly higher in patients with PSI than in other patients. A threshold of 2800 leucocytes/mm3 showed a sensitivity of 87% and a specificity of 88% (AUROC 0.92). Microbiological cultures showed a sensitivity of 76% and a specificity of 100%.

CONCLUSIONS

A threshold of 2800 leucocytes/mm3 in synovial fluid can be recommended to predict PSI. Microbiological culture has an excellent specificity and allows for targeted antibiotic therapy. Joint aspiration presents an important pillar to diagnose PSI.

Diagnostic Value of Next-Generation Sequencing in Periprosthetic Joint Infection: A Systematic Review

Next‐generation sequencing (NGS) has developed rapidly in the last decade and is emerging as a promising diagnostic tool for periprosthetic joint infection (PJI). However, its diagnostic value for PJI is still uncertain. This systematic review aimed to explore the diagnostic value of NGS for PJI and verify its accuracy for culture‐negative PJI patients. We conducted this systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta‐Analysis (PRISMA) guidelines. Medline, Embase, and Cochrane Library were searched to identify diagnostic technique studies evaluating the accuracy of NGS in the diagnosis of PJI. The diagnostic sensitivity, specificity, and positive and negative predictive values were estimated for each article. The detection rate of NGS for culture‐negative PJI patients or PJI patients with antibiotic administration history was also calculated. Of the 87 identified citations, nine studies met the inclusion criteria. The diagnostic sensitivities and specificities of NGS ranged from 63% to 96% and 73% to 100%, respectively. The positive and negative predictive values ranged from 71% to 100% and 74% to 95%, respectively. The detection rate of NGS for culture‐negative PJI patients in six studies was higher than 50% (range from 82% to 100%), while in three studies it was lower than 50% (range from 9% to 31%). Also, the detection rate of NGS for PJIs with antibiotic administration history ranged from 74.05% to 92.31%. In conclusion, this systematic review suggests that NGS may have the potential to be a new tool for the diagnosis of PJI and should be considered to be added to the portfolio of diagnostic procedures. Furthermore, NGS showed a favorable diagnostic accuracy for culture‐negative PJI patients or PJI patients with antibiotic administration history. However, due to the small sample sizes of studies and substantial heterogeneity among the included studies, more research is needed to confirm or disprove these findings.

Comparative meta-omics for identifying pathogens associated with prosthetic joint infection

Prosthetic joint infections (PJI) are economically and personally costly, and their incidence has been increasing in the United States. Herein, we compared 16S rRNA amplicon sequencing (16S), shotgun metagenomics (MG) and metatranscriptomics (MT) in identifying pathogens causing PJI. Samples were collected from 30 patients, including 10 patients undergoing revision arthroplasty for infection, 10 patients receiving revision for aseptic failure, and 10 patients undergoing primary total joint arthroplasty. Synovial fluid and peripheral blood samples from the patients were obtained at time of surgery. Analysis revealed distinct microbial communities between primary, aseptic, and infected samples using MG, MT, (PERMANOVA p = 0.001), and 16S sequencing (PERMANOVA p < 0.01). MG and MT had higher concordance with culture (83%) compared to 0% concordance of 16S results. Supervised learning methods revealed MT datasets most clearly differentiated infected, primary, and aseptic sample groups. MT data also revealed more antibiotic resistance genes, with improved concordance results compared to MG. These data suggest that a differential and underlying microbial ecology exists within uninfected and infected joints. This study represents the first application of RNA-based sequencing (MT). Further work on larger cohorts will provide opportunities to employ deep learning approaches to improve accuracy, predictive power, and clinical utility.

Comparative study of culture, next-generation sequencing, and immunoassay for identification of pathogen in diabetic foot ulcer

Treatment of deep musculoskeletal infection (MSKI) begins with accurate identification of the offending pathogen, surgical excision/debridement, and a course of culture-directed antibiotics. Despite this, the incidence of recurrent infection continues to rise. A major contributor to this is inaccurate or negative initial cultures. Accurate identification of the main pathogen is paramount to treatment success. This is especially important in treating diabetic foot infections (DFIs) with limb salvage efforts. This study seeks to utilize standard culture, next-generation sequencing (NGS), and immunoassay for newly synthesized antibodies (NSA) to Staphylococcus aureus and Streptococcus agalactiae for diagnosis. This is a level II prospective observational study approved by our IRB. Thirty patients > 18 years of age who presented with a DFI and underwent surgical debridement or amputation by a single academic orthopedic surgeon from October 2018 to September 2019 were enrolled. Intraoperative samples were obtained from the base of the wound and sent for culture, NGS, and a peripheral blood sample was obtained at the time of diagnosis. NGS and culture were highly correlated for S. aureus (κ = 0.86) and S. agalactiae (κ = 1.0), NSA immunoassay and culture demonstrated a fair correlation for S. aureus (κ = 0.18) and S. agalactiae (κ = 0.67), and NGS and NSA immunoassay demonstrated fair correlation for S. aureus (κ = 0.1667) and S. agalactiae (κ = 0.67). Our study demonstrates a high concordance between culture and NGS in identifying the dominant pathogen in DFU. NGS may be a useful adjunct in DFI diagnosis.

Future potential of metagenomics in clinical laboratories

INTRODUCTION

Rapid and sensitive diagnostic strategies are necessary for patient care and public health. Most of the current conventional microbiological assays detect only a restricted panel of pathogens at a time or require a microbe to be successfully cultured from a sample. Clinical metagenomics next-generation sequencing (mNGS) has the potential to unbiasedly detect all pathogens in a sample, increasing the sensitivity for detection and enabling the discovery of unknown infectious agents.

AREAS COVERED

High expectations have been built around mNGS; however, this technique is far from widely available. This review highlights the advances and currently available options in terms of costs, turnaround time, sensitivity, specificity, validation, and reproducibility of mNGS as a diagnostic tool in clinical microbiology laboratories.

EXPERT OPINION

The need for a novel diagnostic tool to increase the sensitivity of microbial diagnostics is clear. mNGS has the potential to revolutionise clinical microbiology. However, its role as a diagnostic tool has yet to be widely established, which is crucial for successfully implementing the technique. A clear definition of diagnostic algorithms that include mNGS is vital to show clinical utility. Similarly to real-time PCR, mNGS will one day become a vital tool in any testing algorithm.

Application of ica D, eno, sar A and agr gene testing in early diagnosis of periprosthetic joint infection

Objective This study intends to explore the diagnostic efficiency and value of PCR in the early diagnosis of periprosthetic joint infection (PJI) based on the testing of the four staphylococcal specific genes ica D, eno, sar A and agr. Methods 41 samples of ultrasonic cleavage RNA eluate were extracted from the human joint model of PJI caused by the five most common PJI pathogens to detect the PCR of ica D, eno, sar A and agr genes. Based on the detection results, the sensitivity, specificity, positive and negative predictive value and accuracy of the four genes were analyzed and compared. Results eno test had a high sensitivity (83.33%). However, more false positive results affected the test specificity (47.06%); sar A test did not show false positive results, but the specificity was high (100%), but the sensitivity was low (41.67%); the sensitivity of ica D and agr test was 4.17% and 0%, respectively, and the clinical value was limited. Conclusion eno and sar A gene detection is of high value in early diagnosis of PJI. Reasonable design and sequential application of eno sensitivity preliminary diagnosis and sar A specific screening of false positive results are more beneficial to the early diagnosis of staphylococcal pathogenic PJI.

Diagnostic accuracy of multiplex polymerase chain reaction on tissue biopsies in periprosthetic joint infections

The diagnosis and treatment of periprosthetic joint infection (PJI) currently relies on cultures, which are time-consuming and often fail. Multiplex PCR assays promise reliable and prompt results, but have been heterogeneously evaluated. In this study, we analyse multiplex PCR in pathogen identification using only tissue biopsies. 42 patients after revision arthroplasty of the hip or knee were evaluated using multiplex PCR to identify microorganisms. The patients were classified according to the diagnostic criteria published by Zimmerli et al. and the results were compared to the respective microbiological cultures. PJI was detected in 15 patients and 27 revisions were aseptic. The multiplex PCR of tissue biopsies had a sensitivity of 0.3 (95% CI 0.12-0.62), a specificity of 1.0 (0.87-1.0), a positive predictive value of 1.0 (0.48-1.0) and a negative predictive value of 0.73 (0.56-0.86). The diagnostic accuracy of multiplex PCR on tissue biopsy samples is low in comparison to routine microbiological cultures. The evaluation of tissue biopsies using multiplex PCR was prone to false negative results. However, multiplex PCR assays have the advantage of rapid pathogen identification. We therefore recommend further investigation of multiplex PCR in the setting of suspected PJI with a careful choice of specimens.

sCD28, sCD80, sCTLA-4, and sBTLA Are Promising Markers in Diagnostic and Therapeutic Approaches for Aseptic Loosening and Periprosthetic Joint Infection

Aseptic prosthetic loosening and periprosthetic joint infections (PJI) are among the most frequent complications after total knee/hip joint arthroplasty (TJA). Current research efforts focus on understanding the involvement of the immune system in these frequent complications. Different immune cell types have already been implicated in aseptic prosthetic loosening and PJI. The aim of this study was to systematically analyze aspirates from knee and hip joints, evaluating the qualitative and quantitative composition of soluble immunoregulatory markers, with a focus on co-inhibitory and co-stimulatory markers. It has been shown that these molecules play important roles in immune regulation in cancer and chronic infectious diseases, but they have not been investigated in the context of joint replacement. For this purpose, aspirates from control joints (i.e., native joints without implanted prostheses), joints with TJA (no signs of infection or aseptic loosening), joints with aseptic implant failure (AIF; i.e., aseptic loosening), and joints with PJI were collected. Fourteen soluble immunoregulatory markers were assessed using bead-based multiplex assays. In this study, it could be shown that the concentrations of the analyzed immunoregulatory molecules vary between control, TJA, AIF, and PJI joints. Comparing TJA patients to CO patients, sCD80 was significantly elevated. The marker sBTLA was significantly elevated in AIF joints compared to TJA joints. In addition, a significant difference for eight markers could be shown when comparing the AIF and CO groups (sCD27, sCTLA-4, sCD137, sCD80, sCD28, sTIM-3, sPD-1, sBTLA). A significant difference was also reached for nine soluble markers when the PJI and CO groups were compared (sLAG-3, sCTLA-4, sCD27, sCD80, sCD28, sTIM-3, sPD-1, IDO, sBTLA). In summary, the analyzed immunoregulatory markers could be useful for diagnostic purposes as well as to develop new therapeutic approaches for AIF and PJI.

Adherence to a reliable PJI diagnostic protocol minimizes unsuspected positive cultures rate

BACKGROUND

The aim of the present study was to evaluate the incidence of unsuspected PJI when prosthetic revisions are thoroughly evaluated by PJI dedicated orthopedic surgeon before surgery. The hypothesis is that the incidence of unsuspected PJI is reduced by applying this protocol.

METHODS

This is a historical cohort study carried out in one university hospital. The prosthetic revision assessment was carried out in January 2019. From that date on, all patients that were programmed for hip or knee revision (either by an orthopedic surgeon specialized or not in septic revisions) were scheduled for a preoperative visit with the same orthopedic surgeon specialized in septic revisions. The diagnostic algorithm applied was based on the Pro-Implant Foundation diagnostic criteria. Prior to the revision assessment, the indication for joint aspiration was done at the surgeons' discretion (non-specialized in septic revisions) and the preoperative identification of PJI was also done by a hip or knee surgeon (not specialized in septic surgery).

RESULTS

Based on the PIF criteria, there were 15 infections among the revisions in group 1 and 18 PJI in group 2 (p > 0.05). The most interesting finding was that there were 7 patients with unsuspected positive cultures in group 1. That represents 11% of all revisions. No patient in group 2 was found with unsuspected positive cultures (p < 0.001).

CONCLUSION

A thorough PJI diagnostic algorithm should be implemented before prosthetic revision to avoid unsuspected positive cultures.