Synovial Fluid-Induced Aggregation Occurs across Staphylococcus aureus Clinical Isolates and is Mechanistically Independent of Attached Biofilm Formation.

Rapid synovial fluid-induced aggregation of Staphylococcus aureus is currently being investigated as an important factor in the establishment of periprosthetic joint infections (PJIs). Pathogenic advantages of aggregate formation have been well documented in vitro, including recalcitrance to antibiotics and protection from host immune defenses. The objective of the present work was to determine the strain dependency of synovial fluid-induced aggregation by measuring the degree of aggregation of 21 clinical S. aureus isolates cultured from either PJI or bloodstream infections using imaging and flow cytometry. Furthermore, by measuring attached bacterial biomass using a conventional crystal violet assay, we assessed whether there is a correlation between the aggregative phenotype and surface-associated biofilm formation. While all of the isolates were stimulated to aggregate upon exposure to bovine synovial fluid (BSF) and human serum (HS), the extent of aggregation was highly variable between individual strains. Interestingly, the PJI isolates aggregated significantly more upon BSF exposure than those isolated from bloodstream infections. While we were able to stimulate biofilm formation with all of the isolates in growth medium, supplementation with either synovial fluid or human serum inhibited bacterial surface attachment over a 24 h incubation. Surprisingly, there was no correlation between the degree of synovial fluid-induced aggregation and quantity of surface-associated biofilm as measured by a conventional biofilm assay without host fluid supplementation. Taken together, our findings suggest that synovial fluid-induced aggregation appears to be widespread among S. aureus strains and mechanistically independent of biofilm formation. IMPORTANCE Bacterial infections of hip and knee implants are rare but devastating complications of orthopedic surgery. Despite a widespread appreciation of the considerable financial, physical, and emotional burden associated with the development of a prosthetic joint infection, the establishment of bacteria in the synovial joint remains poorly understood. It has been shown that immediately upon exposure to synovial fluid, the viscous fluid in the joint, Staphylococcus aureus rapidly forms aggregates which are resistant to antibiotics and host immune cell clearance. The bacterial virulence associated with aggregate formation is likely a step in the establishment of prosthetic joint infection, and as such, it has the potential to be a potent target of prevention. We hope that this work contributes to the future development of therapeutics targeting synovial fluid-induced aggregation to better prevent and treat these infections.

Incidence of Cutibacterium acnes in open shoulder surgery.

In recent years, Cutibacterium acnes (C. acnes) has been reported to affect postoperative outcomes. The purpose of this study was to examine the detection rate and clinical features of C. acnes infection after open shoulder surgery. Fifty-nine patients (33 males and 26 females; mean age, 69.1 years) were included. Samples were collected from a skin swab at the incision site prior to skin preparation. Further samples were collected from synovial swabs at the glenohumeral joint immediately after incision and before incision closure. Samples with C. acnes-positive skin swab cultures were defined as Group A, and those with negative cultures were defined as Group N. Age, sex, presence of diabetes mellitus, operation time, presence of deep infection after surgery, and rate of positive synovial swab cultures were compared between groups. There were 27 patients in Group A (mean age 69.1±13.3 [SD], 21 males and 6 females) and 32 patients in Group N (mean age 69.1±11.0 [SD], 12 males and 20 females). No significant difference in the presence of diabetes mellitus and operation time were found between groups. From the glenohumeral joint immediately after incision, C. acnes was detected in 22.2% and 0% of patients in Group A and Group N, respectively. For the glenohumeral joint before incision closure, C. acnes was detected in 22.2% and 0% of patients in Group A and Group N, respectively, demonstrating a significantly higher rate in Group A. Our findings suggest that the route of infection following open shoulder surgery is via contamination.

Next-generation sequencing for diagnosis of infection: is more sensitive really better?

BACKGROUND: The utility of next-generation sequencing (NGS) in differentiating between active infection and contaminant or baseline flora remains unclear. The purpose of this study is to compare NGS with culture-based methods in primary shoulder arthroplasty. METHODS: A prospective series of primary shoulder arthroplasty patients with no history of infection or antibiotic use within 60 days of surgery was enrolled. All patients received standard perioperative antibiotics. After skin incision, a 10 × 3-mm sample of the medial skin edge was excised. A 2 × 2-cm synovial tissue biopsy was taken from the rotator interval after subscapularis takedown. Each sample set was halved and sent for NGS and standard cultures. RESULTS: Samples from 25 patients were analyzed. Standard aerobic/anaerobic cultures were positive in 10 skin samples (40%, 95% confidence interval [CI] 20%-60%) and 3 deep tissue samples (12%, 90% CI 1%-23%]). NGS detected ≥1 bacterial species in 17 of the skin samples (68%, 95% CI 49%-87%) and 7 deep tissue samples (28%, 95% CI 9%-47%). There was a significant difference (P < .03) in the mean number of bacterial species detected with NGS between the positive standard culture (1.6 species) and the negative standard culture groups (5.7 species). CONCLUSION: NGS identified bacteria at higher rates in skin and deep tissue samples than standard culture did in native, uninfected patients undergoing primary procedures. Further research is needed to determine which NGS results are clinically relevant and which are false positives before NGS can be reliably used in orthopedic cases.

Diagnostic Arthroscopy for Detection of Periprosthetic Infection in Painful Shoulder Arthroplasty.

PURPOSE: To analyze the utility of arthroscopic biopsies for detection of periprosthetic infection in painful shoulder arthroplasty without objective signs of infection. METHODS: A retrospective analysis of all patients who underwent a diagnostic arthroscopy for painful shoulder arthroplasty from June 2012 through July 2018 was performed. Patients with a subsequent revision shoulder arthroplasty after diagnostic arthroscopy were included. Arthroscopic tissue culture results were compared with the culture results of intraoperative tissue samples obtained at the time of open revision surgery. A minimum of 3 tissue samples from synovia and bone-prosthesis interface with signs of synovitis or abnormal appearance was routinely collected. Cases with 2 or more positive cultures for the same microorganism obtained at open revision surgery were considered as true presence of infection. The study protocol was reviewed and approved by the institutional ethics committee. RESULTS: Twenty-three cases in 22 patients were included in this study. Five of these 23 cases were classified as true infection based on the samples obtained during open revision surgery, and 16 cases had a positive culture in diagnostic arthroscopy. Cutibacterium acnes was isolated in each case. Classifying any microbiologic growth in the arthroscopic biopsies as positive resulted in a sensitivity and negative predictive value of 100%, specificity of 39%, and positive predictive value of 31.3% for the detection of a periprosthetic shoulder infection (PPSI). If at least 2 positive samples with the same microbiologic growth in the arthroscopic biopsies were considered as positive, sensitivity and negative predictive value dropped to 80% and 94.4%, respectively, but the specificity and positive predictive value increased to 94.4% and 80%, respectively. CONCLUSIONS: Diagnostic arthroscopy is a useful diagnostic tool in patients with suspicion but no clear evidence of PPSI. Arthroscopically obtained tissue biopsies for culture offer a high sensitivity and specificity in the diagnosis of PPSI if at least 2 cultures positive for the same microorganism are considered as infection. LEVEL OF EVIDENCE: Level III.

Inflammatory arthritis and Mycobacterium Tuberculosis infection: a diagnostic and management challenge for Knee arthroplasty in endemic areas.

Tuberculosis continues to be one of the most challenging health problems more prevalent in developing countries. Pakistan ranks 5th in tuberculosis prevalence among the high-burden countries. Prosthetic joint infection of the knee by acid fast bacilli is a rare and distressing complication, occurring in nearly 1% of primary joint arthroplasties requiring prolonged medical treatment and multiple surgeries. A recent publication extensively reviewed English literature from 1952 to 2016, and repor ted only 64 prosthetic joint infec tion with tuberculosis, of which 27 cases involved the knee. Tuberculosis is a global health problem adding to the challenges that arthroplasty surgeons face in our resource-constrained setting. Furthermore, it presents as other inflammatory arthritis with almost same laboratory and radiological findings. The current paper was planned to highlight the preoperative and postoperative challenges that the arthroplasty surgeon may have in diagnosis and management of this rare infection. We included studies from 1996 to date which reported knee tuberculosis prosthetic joint infection that were managed by medication alone or with surgical intervention in patients who had undergone arthroplasty.

No evidence of Chlamydia pneumoniae in the synovia of patients with osteoarthritis.

OBJECTIVE: Osteoarthritis (OA) is a common cause of disability affecting millions of people of all ages worldwide. The pathogenesis involves an inflammatory component, but the cause of the inflammation remains incompletely understood. The intracellular bacteria Chlamydia trachomatis and C. pneumoniae have been demonstrated in patients with reactive arthritis. Both of these microorganisms can cause chronic and persistent infections, with C. trachomatis being the most common cause of reactive arthritis. This study was performed to investigate the presence of C. pneumoniae in a large number of patients with primary OA. METHODS: The study included 75 patients who underwent total knee arthroplasty. During surgery, a synovial biopsy was performed and synovial fluid drawn. Real-time polymerase chain reaction (PCR) of C. pneumoniae was run on all patients, and real-time PCR of bacterial 16S rDNA was conducted on 30 of the 75 patients to screen for the presence of other bacteria. RESULTS: Real-time PCR showed no evidence of the presence of C. pneumoniae in the patients' specimens, nor were other bacteria detected. CONCLUSIONS: Although an inflammatory component is part of the pathogenesis of OA, we found no evidence indicating that C. pneumoniae is a stimulator of that inflammation.

Usefulness of Culturing the Periprosthetic Membrane or Neosynovium for the Diagnosis of Infection During Hip and Knee Revision Arthroplasty.

INTRODUCTION: Identification of microorganisms is critical for correct management of an infected arthroplasty. Our hypothesis is that the culture yield depends on the location around the prosthesis from which samples are obtained. METHODS: This prospective study included 298 revisions of the hip (123) and knee (175). We compared the yield of the intraoperative samples obtained, which included synovial fluid (two), neosynovium (two), and periprosthetic membrane (two). RESULTS: Cultures were positive in 28 cases, in which 15 had the same diagnosis considering either the neosynovium or the membrane, and there were 3 cases in which the infection could have been diagnosed only by considering the combination of both. In all, there were 8 cases in which the infection might have been misdiagnosed unless considering a combination of both solid tissue samples (P = 0.004). CONCLUSIONS: The yields of the periprosthetic membrane and neosynovium do not differ significantly, and we recommend considering a combination of both. LEVEL OF EVIDENCE: Diagnostic Level II.

High-sensitivity virus and mycoplasma screening test reveals high prevalence of parvovirus B19 infection in human synovial tissues and bone marrow.

BACKGROUND: Latent microorganism infection is a safety concern for the clinical application of mesenchymal stem cells (MSCs). The aim of this study is to investigate the frequencies and sensitivities of the latent virus and mycoplasma infections in synovium, bone marrow, peripheral blood cells, and blood plasma and cultured synovial MSCs. METHODS: Total DNA and RNA of the synovium (n = 124), bone marrow (n = 123), peripheral blood cells (n = 121), plasma (n = 121), and 14-day cultured synovial MSCs (n = 63) were collected from patients who underwent total knee arthroplasty or anterior ligament reconstruction after written informed consents were obtained. The multiplex polymerase chain reaction (PCR) primers were designed to quantitatively measure the representative genomes of 13 DNA viruses, 6 RNA viruses, and 9 mycoplasmas. Multi-spliced mRNA detection and virus spike test were also performed to demonstrate the sensitivity of synovial MSCs to the candidate pathogens. RESULTS: In synovium and bone marrow, the positive rates of parvovirus B19 genome were significantly higher than in peripheral blood cells (18.7% and 22% vs. 0.8%, respectively). Multi-alignment analysis of amplified and sequenced viral target genes showed the proximity of the parvovirus B19 gene from different tissue in the same patients. Synovial MSCs cultured for 14 days were positive for virus infection only in two patients (2/62 = 3%). Parvovirus B19 multi-spliced mRNAs were not detected in these two samples. Virus spike test demonstrated the sensitivity of synovial MSCs to herpes simplex virus (HSV)1 and cytomegalovirus (CMV), but not to parvovirus B19. CONCLUSION: This study revealed a relatively high incidence of latent parvovirus B19 in synovium and bone marrow tissue.

Role of Th17 and Treg cells in septic arthritis and the impact of the Th17/Treg -derived cytokines in the pathogenesis of S. aureus induced septic arthritis in mice.

Intravenous inoculation of Swiss mice with S. aureus leads to severe synovial joint tissue swelling along with prominent T lymphocyte infiltrate with associated inflammation in synovial tissue. Cytokines released from macrophages such as TNF-α, IL-1ß and IL-6 the main players that precede cartilage and bone destruction during septic arthritis (SA) followed by osteoclast differentiation and bone resorption. CD4+ naïve T cells upon cytokine driven activation, differentiate into lineages of helper (Th) and regulatory T cells (Treg) including inflammatory Th17 cell lineage. Acting as counterbalance, Tregs protect the host by releasing anti-inflammatory IL-10. A disturbed balance between Th17 and Treg cell development skews the pathways towards Th17 lineage, but how it actually induces SA is still unexplored. Therefore, this study has been attempted to demonstrate the Th17/Treg ratio in synovial tissue, spleen and peripheral blood by FACS and their derived cytokines from serum of arthritic mice. Here, we reported that the ratios of Th17/Treg as well as their related cytokine levels were increased at 3 days post-infection which was decreased during 9 DPI but heightened again at 15DPI resulting in persistence of the disease, though decreased again at 30 DPI even in animals with increased dose of infection. Bacterial colonies were present in synovial joints at 15 DPI in animals with increased infection but found to be absent at 30 DPI. Maintaining Th17/Treg balance by neutralizing functionally active Th17 and their related cytokines or adoptive transfer of fully active Tregs and/or their related cytokines may lead to a novel therapeutic strategy for combating Staphylococcal arthritis.

Contamination risk of synovial biopsy cultures in total hip arthroplasty: a prospective review of 100 cases.

INTRODUCTION: Cultures of deep synovial biopsies remain an important tool in diagnosing periprosthetic joint infection, a devastating complication following total hip arthroplasty (THA). Recent reports of unexpected positive intraoperative cultures in aseptic revision arthroplasty, however, challenge the validity and interpretation of these cultures. The aim of this study was to evaluate the contamination risk of synovial biopsy cultures collected intraoperatively during primary THA of healthy subjects. METHODS: Synovial biopsies for culture were collected during primary total hip arthroplasty procedures from 100 consecutive cases. The synovial biopsies were taken within the first 15 minutes after skin incision. Biopsy specimen were cultured on 4 different media for 8 or 15 days. Positive cultures were identified using Maldi-Tof spectrometry. RESULTS: 16 cultures yielded a bacterium, suggesting a false positive result of 16%. The mean time for the cultures to become positive was 6.29 days (standard deviation [SD] 3.90) with a maximum of 15 days. Proprionibacterium acnes and Staphylococcus epidermidis were most commonly cultured with 6 positive results for both bacteria. CONCLUSIONS: Our study yielded a 16% false positive rate in cultures of synovial biopsy taken during primary total hip arthroplasty of healthy subjects, suggesting that contamination risk of these synovial biopsy cultures may be larger than assumed by clinicians.

Pre-operative intra-articular deep tissue sampling with novel retrograde forceps improves the diagnostics in periprosthetic joint infection.

BACKGROUND: Histopathological tissue analysis is a key parameter within the diagnostic algorithm for suspected periprosthetic joint infections (PJIs), conventionally acquired in open surgery. In 2014, Hügle and co-workers introduced novel retrograde forceps for retrograde synovial biopsy with simultaneous fluid aspiration of the knee joint. We hypothesised that tissue samples acquired by retrograde synovial biopsy are equal to intra-operatively acquired deep representative tissue samples regarding bacterial detection and differentiation of periprosthetic infectious membranes. METHOD: Thirty patients (male n = 15, 50%; female n = 15, 50%) with 30 suspected PJIs in painful total hip arthroplasties (THAs) were included in this prospective, controlled, non-blinded trial. The results were compared with intra-operatively obtained representative deep tissue samples. RESULTS: In summary, 27 out of 30 patients were diagnosed correctly as infected (17/17) or non-infected (10/13). The sensitivity to predict a PJI using the Retroforce® sampling forceps in addition to standard diagnostics was 85%, the specificity 100%. CONCLUSIONS: Retrograde synovial biopsy is a new and rapid diagnostic procedure under local anaesthesia in patients with painful THAs with similar histological results compared to deep tissue sampling.

A diagnosis of disseminated tuberculosis based on knee arthroscopic guided synovial biopsy in the context of monoarthritis.

Accounting for 2.2-4.7% of all tuberculosis cases in Europe and USA and around 10-15% of extra-pulmonary tuberculosis cases, osteoarticular tuberculosis tends to be chronic, slowly progressive and destructive. We report the case of an 81-year-old male with 3 weeks of progressively worsening pain, swelling and limited range of motion of the left knee. A knee arthroscopy was performed for synovial biopsy at our department revealing diffuse synovitis with scarce villi formation. The positive polymerase chain reaction assay for Mycobacterium tuberculosis in the synovial tissue allowed the establishment of the diagnosis and synovium histology showed caseating granulomas. A lengthy delay between first symptoms of osteoarticular tuberculosis and the beginning of treatment has been reported. A high index of suspicion, synovial membrane biopsy and appropriate microbiologic testing are fundamental to avoid a delay in diagnosis.

Intraoperative synovial C-reactive protein is as useful as frozen section to detect periprosthetic hip infection.

BACKGROUND: Synovial quantification of C-reactive protein (SCRP) has been recently published with high sensitivity and specificity in the diagnosis of periprosthetic joint infection. However, to our knowledge, no studies have compared the use of this test with intraoperative frozen section, which is considered by many to be the best intraoperative test now available. QUESTIONS/PURPOSES: We asked whether intraoperative SCRP could lead to comparable sensitivity, specificity, and predictive values as intraoperative frozen section in revision total hip arthroplasty. METHODS: A prospective study was performed including 76 patients who underwent hip revision for any cause. SCRP quantification (using 9.5 mg/L as denoting infection) and the analysis of frozen section of intraoperative samples (five or more polymorphonuclear leukocytes under high magnification in 10 fields) were performed in all the patients. The definitive diagnosis of an infection was determined according to the Musculoskeletal Infection Society (MSIS). In this group, 30% of the patients were diagnosed with infection using the MSIS criteria (23 of 76 patients). RESULTS: With the numbers available, there were no differences between SCRP and frozen section in terms of their ability to diagnose infection. The sensitivity of SCRP was 90% (95% confidence interval [CI], 70.8%-98.6%), the specificity was 94% (95% CI, 84.5%-98.7%), the positive predictive value was 87% (95% CI, 66.3%-97%), and the negative predictive value was 96% (95% CI, 87%-99.4%); the sensitivity, specificity, positive predictive value, and negative predictive value were the same using frozen sections to diagnose infection. The positive likelihood ratio was 16.36 (95% CI, 5.4-49.5), indicating a low probability of an individual without the condition having a positive test, and the negative likelihood ratio was 0.10 (95% CI, 0.03-0.36), indicating low probability of an individual without the condition having a negative test. CONCLUSIONS: We found that quantitative SCRP had similar diagnostic value as intraoperative frozen section with comparable sensitivity, specificity, and predictive value in a group of patients undergoing revision total hip arthroplasty. In our institution, SCRP is easier to obtain, less expensive, and less dependent on the technique of obtaining and interpreting a frozen section. If our findings are confirmed by other groups, we suggest that quantitative SCRP be considered as a viable alternative to frozen section. LEVEL OF EVIDENCE: Level I, diagnostic study.

Toll-like receptor 2 and 6 interdependency in the erosive stage of Staphylococcus aureus induced septic arthritis mediated by IFN-γ and IL-6--A possible involvement of IL-17 in the progression of the disease.

Staphylococcus aureus induced septic arthritis has emerged as a potent disabling and life threatening disease; hence combating this malady has become an imperative need of medical science. Role of TLR-2 in innate recognition of S. aureus and activation of inflammatory cascade by the interplay of some proinflammatory cytokines, resulting in joint inflammation has been established. Variation in the reports suggesting both functional dependency and independency of TLR-2 on its heterodimeric partner TLR-6 in response to ligands exists, thus this study was postulated to observe the expression pattern of TLR-6 in synovial tissue and lymphoid organs after inducing septic arthritis by S. aureus in Swiss albino mouse model and the instigated cytokine profile could affirm its plausible role in SA. The functional relation of TLR-2 and 6 was verified by simulating an in vitro study design on synovial mononuclear cells, blocking TLR-2 and 6, and it was found that they are required to co-express for generating cytokine, NO and H2O2 on infection. IFN-γ, IL-6 and IL-17 were identified to play a distinguished role in SA from their secretion pattern in both in vivo and in vitro study. IFN-γ and IL-6 remained high throughout the infection possibly by the shift of response from Th1 to Th2 and Th17 and contribute in various converging pathways of inflammation. IL-17 increased with the onset of the disease but reduced on the late period. Hence IFN-γ, IL-6, IL-17 along with TLR-6 can be a potent target for therapeutic approach because of their significant contribution in SA.

[Molecular pathological diagnostics of infections in orthopedic pathology]. / Molekularpathologische Infektionsdiagnostik in der orthopädischen Pathologie.

The diagnosis of infections in patients with arthritis and/or in joint prostheses requires interdisciplinary cooperation and the application of up-to-date methods. The histological investigation of the synovial membrane allows the differentiation of acute, chronic and granulomatous synovialitis. Detection of conserved regions of the microbial genome by PCR, especially 16S rRNA for bacteria and 18S rRNA for fungi, is a broad approach for the classification of pathogens which cannot be cultured. Acute infectious arthritis and periprosthetic infections share the spectrum of pathogens with sepsis, therefore multiplex PCR-based methods for the detection of sepsis can be employed. Molecular diagnostics can detect minimal infections in periprosthetic tissues even after antibiotic therapy. The anamnesis (enteral or urogenital infection), clinical picture (oligoarthritis) and further parameters (e.g. HLA B27 status) are important for the diagnosis of reactive arthritis. In many cases of reactive arthritis, molecular methods allow the detection of bacterial DNA or RNA in synovial fluid or tissue samples. The low sensitivity of histopathological methods may be compensated by application of PCR techniques, especially in the differential diagnosis of granulomatous synovitis including mycobacterial infections. Molecular methods can be used to support the differential diagnosis of septic and reactive arthritis. MicroRNA techniques combined with PCR for detection of pathogens support the differential diagnosis of rheumatoid arthritis with severe inflammatory activity compared to infectious arthritis. Proteomic methods could expand the methodological spectrum for the diagnosis of infections.

[Septic arthritis in adults]. / Septische Arthritis des Erwachsenen.

Septic arthritis is a true rheumatological emergency requiring immediate and thoughtful effort for rapid diagnosis establishment and treatment initiation. Children and elderly persons as well as immunocompromised individuals, patients with pre-existing joint damage and with inflammatory rheumatic joint diseases are preferentially affected. Bacteremia, joint surgery and intra-articular injections pose risk situations for the development of joint infections. The most frequent causative organism is Staphylococcus aureus but other relevant pathogens include coagulase-negative staphylococci, streptococci and mycobacteria. Synovial fluid analysis (e.g. appearance, cell count and microbiological examination) is the most important step to establish the diagnosis. The two main components of therapy consist of joint drainage and antibiotic treatment. The approach to periprosthetic joint infections depends on the duration of symptoms, causative organism and individual factors.

Clinical and microbiological findings in prosthetic joint replacement due to aseptic loosening.

OBJECTIVES: A role for microorganisms in aseptic prosthetic loosening (AL) is postulated. We analyse the microbiological and clinical findings of patients with suspected AL, and compare them with patients with chronic prosthetic joint infection (PJI). METHODS: Prospective study (2011-2012) of patients with presumed AL. Evaluation of tissue samples (≥5; TS) at the time of surgery and sonication fluid (SF) of prosthesis. RESULTS: According to positive culture in TS/SF, 89 patients were divided into: Group1: (≥2 positive-TS; n = 12); Group2: single positive-TS and concordant SF (n = 10); Group3: one positive or non-concordant TS or SF (n = 38); and Group4: cultures negative (n = 29). Positive-SF was always concordant with TS in Group 1 (75%); it was positive in 74% in Group 3. Median months (prosthesis-age: implantation to revision arthroplasty) for PJI and Group 1-4 was 21, 46, 65, 63 and 81, respectively (P < 0.001); they also had a different dynamic trend in prosthesis failure (P < 0.001). CONCLUSIONS: Several patients with suspected AL are misdiagnosed PJI. Results from SF correlated well with TS in Group 1, led us to consider single positive-TS as significant (Group 2) and to suggest that microorganisms were on the prosthesis (Group 3). We observed a correlation between microbiology and prosthesis-age, which supports that early loosening is more often caused by hidden PJI than late loosening.

Utility of percutaneous joint aspiration and synovial biopsy in identifying culture-positive infected hip arthroplasty.

PURPOSE: Percutaneous synovial biopsy has recently been reported to have a high diagnostic value in the preoperative identification of periprosthetic infection of the hip. We report our experience with this technique in the evaluation of patients undergoing revision hip arthroplasty, comparing results of preoperative synovial biopsy with joint aspiration in identifying an infected hip arthroplasty by bacteriological analysis. MATERIALS AND METHODS: We retrospectively reviewed the results of the 110 most recent revision hip arthroplasties in which preoperative synovial biopsy and joint aspiration were both performed. Revision surgery for these patients occurred during the period from September 2005 to March 2012. Using this study group, results from preoperative cultures were compared with preoperative laboratory studies and the results of intraoperative cultures. Synovial aspiration was done using an 18- or 20-gauge spinal needle. Synovial biopsy was done coaxially following aspiration using a 22-gauge Chiba needle or 21-gauge Sure-Cut needle. Standard microbiological analysis was performed on preoperative synovial fluid aspirate and synovial biopsy. Intraoperative tissue biopsy bacteriological analysis results at surgical revision were accepted as the "gold standard" for the presence or absence of infection. RESULTS: Seventeen of 110 (15 %) of patients had intraoperative culture-positive periprosthetic infection. Of these 17 cases, there were ten cases where either the synovial fluid aspiration and/or the synovial biopsy were true positive (sensitivity of 59 %, specificity of 100 %, positive predictive value of 100 % and accuracy of 94 %). There were seven cases where aspiration and biopsy results were both falsely negative, but no false-positive results. Similar results were found for synovial fluid aspiration alone. The results of synovial biopsy alone resulted in the identification of seven infected joints with no false-positive result (sensitivity of 41 %, specificity of 100 %, positive predictive value of 100 %, and accuracy of 91 %). CONCLUSIONS: Standard microbiological analyses performed on percutaneous synovial biopsy specimen during the preoperative evaluation of patients undergoing revision hip arthroplasty did not improve detection of culture-positive periprosthetic infection as compared to synovial fluid aspiration alone.

Effects of Ureaplasma urealyticum lipid-associated membrane proteins on rheumatoid arthritis synovial fibroblasts.

OBJECTIVES: As an infectious agent might play a role in rheumatoid arthritis (RA) development, this study investigated effects of Ureaplasma urealyticum lipid-associated membrane proteins (UuLAMPs) on RA synovial fibroblast (RASF) proliferation, and tumour necrosis factor (TNF)-α and interleukin (IL)-1ß production by THP-1 macrophages. Possible immunogenic proteins in UuLAMPs were identified. METHODS: RASFs were cultured from synovial tissue from donors with RA. Serum samples from donors with/without RA and with/without U. urealyticum infection were used for immunogenicity analyses. THP-1 macrophages served as a model for synovial macrophages. TNF-α and IL-1ß mRNA levels were assessed using reverse transcription-polymerase chain reaction; protein levels were estimated using enzyme-linked immunosorbent assay. UuLAMPs underwent separation and Western blot analyses. RESULTS: UuLAMPs (0.025-0.4 µg/ml) stimulated RASF proliferation in a dose- and time-dependent manner, and increased TNF-α and IL-1ß levels in THP-1 macrophages. Several immunogenic UuLAMPs were identified, but antibodies to a 25 kDa protein were only found in RA patients with U. urealyticum infection. CONCLUSIONS: UuLAMPs might induce RASF proliferation and proinflammatory cytokine secretion in synovium from RA patients. A 25 kDa U. urealyticum protein might act as a cross-reactive antigen.

Porphyromonas gingivalis and the pathogenesis of rheumatoid arthritis: analysis of various compartments including the synovial tissue.

INTRODUCTION: We evaluated the presence of Porphyromonas gingivalis (Pg) DNA in the synovial tissue through synovial biopsy and in other compartments of rheumatoid arthritis (RA) patients in comparison with patients affected by other arthritides. Possible links with clinical, immunologic and genetic features were assessed. METHODS: Peripheral blood (PB), sub-gingival dental plaque, synovial fluid (SF) and synovial tissue samples were collected from 69 patients with active knee arthritis (32 with RA and 37 with other arthritides, of which 14 had undifferentiated peripheral inflammatory arthritis - UPIA). Demographic, clinical, laboratory and immunological data were recorded. The presence of Pg DNA was evaluated through PCR. The HLA-DR haplotype was assessed for 45 patients with RA and UPIA. RESULTS: No differences arose in the positivity for Pg DNA in the sub-gingival plaque, PB and SF samples between RA and the cohort of other arthritides. Full PB samples showed a higher positivity for Pg DNA than plasma samples (11.8% vs. 1.5%, P = 0.04). Patients with RA showed a higher positivity for Pg DNA in the synovial tissue compared to controls (33.3% vs. 5.9%, P <0.01). UPIA and RA patients carrying the HLA DRB1*04 allele showed a higher positivity for Pg DNA in the synovial tissue compared to patients negative for the allele (57.1% vs. 16.7%, P = 0.04). RA patients positive for Pg DNA in the sub-gingival plaque had a lower disease duration and a higher peripheral blood leucocyte and neutrophil count. The presence of Pg DNA did not influence disease activity, disease disability or positivity for autoantibodies. CONCLUSIONS: The presence of Pg DNA in the synovial tissue of RA patients suggests a pathogenic role of the bacterium. The higher positivity of Pg DNA in full peripheral blood and synovial tissue samples compared to plasma and synovial fluid suggests a possible intracellular localization of Pg, in particular in patients positive for HLA-DR4.