Synovial fluid lactic acid. A diagnostic aid in septic arthritis

Bacterial Lipoproteins Shift Cellular Metabolism to Glycolysis in Macrophages Causing Bone Erosion

Belonging to a group of membrane proteins, bacterial lipoproteins (LPPs) are defined by a unique lipid structure at their N-terminus providing the anchor in the bacterial cell membrane. In Gram-positive bacteria, LPPs play a key role in host immune activation triggered through a Toll-like receptor 2 (TLR2)-mediated action resulting in macrophage stimulation and subsequent tissue damage demonstrated in in vivo experimental models. Yet the physiologic links between LPP activation, cytokine release, and any underlying switches in cellular metabolism remain unclear. In this study, we demonstrate that Staphylococcus aureus Lpl1 not only triggers cytokine production but also confers a shift toward fermentative metabolism in bone marrow-derived macrophages (BMDMs). Lpl1 consists of di- and tri-acylated LPP variants; hence, the synthetic P2C and P3C, mimicking di-and tri-acylated LPPs, were employed to reveal their effect on BMDMs. Compared to P3C, P2C was found to shift the metabolism of BMDMs and the human mature monocytic MonoMac 6 (MM6) cells more profoundly toward the fermentative pathway, as indicated by lactate accumulation, glucose consumption, pH reduction, and oxygen consumption. In vivo, P2C caused more severe joint inflammation, bone erosion, and lactate and malate accumulation than P3C. These observed P2C effects were completely abrogated in monocyte/macrophage-depleted mice. Taken together, these findings now solidly confirm the hypothesized link between LPP exposure, a macrophage metabolic shift toward fermentation, and ensuing bone destruction. IMPORTANCE Osteomyelitis caused by S. aureus is a severe infection of the bone, typically associated with severe bone function impairment, therapeutic failure, high morbidity, invalidity, and occasionally even death. The hallmark of staphylococcal osteomyelitis is the destruction of the cortical bone structures, yet the mechanisms contributing to this pathology are hitherto poorly understood. One bacterial membrane constituent found in all bacteria is bacterial lipoproteins (LPPs). Previously, we have shown that injection of purified S. aureus LPPs into wild-type mouse knee joints caused a TLR2-dependent chronic destructive arthritis but failed to elicit such effect in monocyte/macrophage-depleted mice. This observation stirred our interest in investigating the interaction of LPPs and macrophages and analyzing the underlying physiological mechanisms. This ascertainment of LPP-induced changes in the physiology of macrophages provides an important clue in the understanding of the mechanisms of bone disintegration, opening novel avenues to manage the course of S. aureus disease.

Recent advances in prevention, detection and treatment in prosthetic joint infections of bioactive materials

Prosthetic joint infection (PJI) is often considered as one of the most common but catastrophic complications after artificial joint replacement, which can lead to surgical failure, revision, amputation and even death. It has become a worldwide problem and brings great challenges to public health systems. A small amount of microbe attaches to the graft and forms a biofilm on its surface, which lead to the PJI. The current standard methods of treating PJI have limitations, but according to recent reports, bioactive materials have potential research value as a bioactive substance that can have a wide range of applications in the field of PJI. These include the addition of bioactive materials to bone cement, the use of antibacterial and anti-fouling materials for prosthetic coatings, the use of active materials such as bioactive glasses, protamine, hydrogels for prophylaxis and detection with PH sensors and fluorescent-labelled nanoparticles, and the use of antibiotic hydrogels and targeting delivery vehicles for therapeutic purposes. This review focus on prevention, detection and treatment in joint infections with bioactive materials and provide thoughts and ideas for their future applications.

Differential metabolism between biofilm and suspended Pseudomonas aeruginosa cultures in bovine synovial fluid by 2D NMR-based metabolomics

Total joint arthroplasty is a common surgical procedure resulting in improved quality of life; however, a leading cause of surgery failure is infection. Periprosthetic joint infections often involve biofilms, making treatment challenging. The metabolic state of pathogens in the joint space and mechanism of their tolerance to antibiotics and host defenses are not well understood. Thus, there is a critical need for increased understanding of the physiological state of pathogens in the joint space for development of improved treatment strategies toward better patient outcomes. Here, we present a quantitative, untargeted NMR-based metabolomics strategy for Pseudomonas aeruginosa suspended culture and biofilm phenotypes grown in bovine synovial fluid as a model system. Significant differences in metabolic pathways were found between the suspended culture and biofilm phenotypes including creatine, glutathione, alanine, and choline metabolism and the tricarboxylic acid cycle. We also identified 21 unique metabolites with the presence of P. aeruginosa in synovial fluid and one uniquely present with the biofilm phenotype in synovial fluid. If translatable in vivo, these unique metabolite and pathway differences have the potential for further development to serve as targets for P. aeruginosa and biofilm control in synovial fluid.

Synovial fluid pH sensor for early detection of prosthetic hip infections

We describe an implantable sensor developed to measure synovial fluid pH for noninvasive early detection and monitoring of hip infections using standard-of-care plain radiography. The sensor was made of a pH responsive polyacrylic acid-based hydrogel, which expands at high pH and contracts at low pH. A radiodense tantalum bead and a tungsten wire were embedded in the two ends of the hydrogel in order to monitor the change in length of the hydrogel sensor in response to pH via plain radiography. The effective pKa of the hydrogel-based pH sensor was 5.6 with a sensitivity of 3 mm/pH unit between pH 4 and 8. The sensor showed a linear response and reversibility in the physiologically relevant pH range of pH 6.5 and 7.5 in both buffer and bovine synovial fluid solutions with a 30-minute time constant. The sensor was attached to an explanted prosthetic hip and the pH response determined from the X-ray images by measuring the length between the tantalum bead and the radiopaque wire. Therefore, the developed sensor would enable noninvasive detection and studying of implant hip infection using plain radiography.

Elaboration of a new synovial predictive score of septic origin for acute arthritis on the native joint (RESAS)

OBJECTIVE

To establish a new predictive score for the diagnosis of septic arthritis (SA) according to different synovial fluid (SF) variables.

METHODS

First, we analysed the different clinical, biological and SF variables associated with the diagnosis of SA (according to the Newman's criteria) in a monocentric cohort of acute arthritis (<30 days) (n = 233) (SYNOLACTATE cohort). A new score predictive of SA (RESAS) was created using the independent discriminant variables after multivariate analysis. A value was attributed to each variable of the score according to the weighting based on their likelihood ratio for the diagnosis of SA. RESAS performance was then tested on the first cohort (internal validation) and then checked on a second independent cohort (n = 70) (external validation).

RESULTS

After multivariate analysis, four independent variables of the SF were included for RESAS: (i) purulent SF or white blood cells count ≥70 000/mm3; (ii) absence/presence of crystals; (iii) lactate; and (iv) glucose synovial level. RESAS ranged between -4 and +13 points. The performance of RESAS to predicted SA was excellent with area under the curve (AUC)=0.928 (0.877-0.980) in internal validation and AUC=0.986 (0.962-1.00) in external validation. For a RESAS threshold ≥+4, SA was diagnosed with Se=56.0% (0.371-0.733), Sp=98.1% (0.952-0.993), LR+=29.1 (10.4-81.6) in the first cohort and with Se=91.7% (0.646-0.985), Sp=98.3% (0.909-0.997), LR+=53.2 (7.56-373) in the second cohort.

CONCLUSION

RESAS is a new composite score of four SF variables with excellent performance to predicted SA in acute arthritis population.

Diagnostic Accuracy of Synovial Lactate, Polymerase Chain Reaction, or Clinical Examination for Suspected Adult Septic Arthritis

BACKGROUND

Adult septic arthritis can be challenging to differentiate from other causes of acute joint pain. The diagnostic accuracy of synovial lactate and polymerase chain reaction (PCR) remains uncertain.

OBJECTIVE

Our aim was to quantify the diagnostic accuracy of synovial lactate, PCR, and clinical evaluation for adults with possible septic arthritis in the emergency department (ED).

METHODS

We report a prospective sampling of ED patients aged ≥ 18 years with knee symptoms concerning for septic arthritis. Clinicians and research assistants independently performed history and physical examination. Serum and synovial laboratory testing was ordered at the discretion of the clinician. We analyzed frozen synovial fluid specimens for l- and d-lactate and PCR. The criterion standard for septic arthritis was bacterial growth on synovial culture and treated by consultants with operative drainage, prolonged antibiotics, or both. Diagnostic accuracy measures included sensitivity, specificity, likelihood ratios, interval likelihood ratios, and receiver operating characteristic area under the curve.

RESULTS

Seventy-one patients were included with septic arthritis prevalence of 7%. No finding on history or physical examination accurately ruled in or ruled out septic arthritis. Synovial l- and d-lactate and PCR were inaccurate for the diagnosis of septic arthritis. Synovial white blood cell count and synovial Gram stain most accurately rule in and rule out septic arthritis.

CONCLUSIONS

Septic arthritis prevalence in ED adults is lower than reported previously. History and physical examination, synovial lactate, and PCR are inadequate for the diagnosis of septic arthritis. Synovial white blood cell count and Gram stain are the most accurate tests available for septic arthritis.

Performance of a new rapid diagnostic test the lactate/glucose ratio of synovial fluid for the diagnosis of septic arthritis

OBJECTIVE

To evaluate the diagnostic performance of the synovial lactate, glucose and lactate/glucose ratio assay for the diagnosis of septic arthritis.

METHODS

In this monocentric cross-sectional study, synovial fluids were prospectively obtained from patients with acute joint effusion (<30 days) on native joint. Septic arthritis was defined using Newman's criteria. To evaluate diagnostic performance, Receiver Operating Characteristic (ROC) curves with Area under the curve (AUC), Sensitivities (Se), Specificities (Sp), LR+ their 95% confidence intervals were calculated. Synovial fluid cultures with gram staining, crystal analyses, synovial fluid white blood cell counts (WBC), lactate and glucose assays were performed.

RESULTS

A total of 233 synovial fluids were included. 25 patients had septic arthritis and 208 had non-septic arthritis (104 crystal-induced arthritis, 15 RA, 8 SpA, 6 reactive arthritis, and 75 acute arthritis of undifferentiated origin). Synovial lactate/glucose ratio performed higher than the synovial lactate or glucose assay separately (AUC: 0.859 [0.772-0.945]). Best synovial lactate/glucose ratio threshold to differentiate septic arthritis from non-septic arthritis was 5 Se 52% [0.34-0.7], Sp 98.1% [0.95-0.99], LR+ 27.0[9.50-76.00]).

CONCLUSION

The diagnostic performance of synovial lactate/glucose allows septic arthritis to be effectively and very quickly distinguished from other types of arthritis.

Diagnosis and Management of Infectious Arthritis in Children

PURPOSE OF REVIEW

Septic arthritis is limb and life-threatening condition which necessitates rapid diagnosis and treatment. It is important for a medical practitioner to be familiar with this condition. This review summarizes the epidemiology, risk factors, diagnosis and differential diagnosis, complications, as well as treatment and the following-up of this condition.

RECENT FINDINGS

Different causative organisms require unique diagnostic and treatment approaches. Establishing the diagnosis often requires multiple diagnostic modalities, some of which are new and innovative. Differential diagnosis requires excluding non-infectious inflammatory causes, such as reactive arthritis, juvenile rheumatoid arthritis, transient synovitis, and pericapsular pyomyositis. There is no consensus regarding the nature or duration of pharmacological or surgical treatment. Treatment includes administration of appropriate antimicrobial therapy and including the use of steroids and drainage. The most common complications are osteonecrosis of the femoral head and chronic osteomyelitis. Complications of septic arthritis are mostly due to a missed diagnosis. Further studies are required to better evaluate the diagnostic and therapeutic choice.

Utility of point-of-care synovial lactate to identify septic arthritis in the emergency department

BACKGROUND

Synovial lactate is a promising biomarker to distinguish septic from aseptic arthritis. If available as a point-of care test, synovial lactate would be rapidly available to aid the emergency provider in clinical decision making. This study assesses the test characteristics of synovial lactate obtained using an EPOC© point-of-care (POC) analyzer to rapidly distinguish septic from aseptic arthritis in the emergency department.

METHODS

We enrolled a convenience sample of patients with possible septic arthritis presenting to the emergency department at a large urban academic center between October 2016 and April 2018. Enrolled patients underwent arthrocentesis based on the clinical judgment of the treating provider. We obtained synovial lactate levels (SLL) from the POC device. Standard laboratory analysis, synovial fluid culture, emergency and hospital course, operative procedures, antibiotics, and discharge diagnosis were abstracted from the electronic medical record.

RESULTS

Thirty-nine patients undergoing forty separate arthrocentesis procedures were enrolled in this study over the two-year period. The sensitivity and specificity of SLL ≥ 5 mmol/L was 0.55 and 0.76 respectively, with +LR 2.3 and -LR 0.6. The sensitivity and specificity of SLL ≥ 10 mmol/L was 0.27 and 0.97 respectively, with +LR 7.9 and -LR 0.8; SLL ≥ 10 mmol/L performed similarly to overall synovial WBC ≥ 50,000/μL by conventional laboratory testing.

CONCLUSION

It is feasible to obtain a synovial lactate level using the EPOC© POC device. In our study, POC SLL performs similarly to other markers used to diagnose septic arthritis. Further study with larger sample sizes is warranted.

Evaluation and Management of Septic Arthritis and its Mimics in the Emergency Department

Septic arthritis is a dangerous medical condition associated with significant morbidity and mortality. However, the differential diagnosis can be broad with conditions that mimic this disease and require different evaluation and treatment. This narrative review presents the emergency medicine evaluation and management, as well as important medical conditions that may mimic this disease. Septic arthritis commonly presents with monoarticular joint pain with erythema, warmth, swelling, and pain on palpation and movement. Fever is present in many patients, though most are low grade. Blood testing and imaging may assist with the diagnosis, but the gold standard is joint aspiration. Management includes intravenous antibiotics and orthopedic surgery consult for operative management vs. serial aspirations. Clinicians should consider mimics, such as abscess, avascular necrosis, cellulitis, crystal-induced arthropathies, Lyme disease, malignancy, osteomyelitis, reactive arthritis, rheumatoid arthritis, and transient synovitis. While monoarticular arthritis can be due to septic arthritis, other medical and surgical conditions present similarly and require different management. It is essential for the emergency clinician to be aware how to diagnose and treat these mimics.

Clinical use of plasma lactate concentration. Part 2: Prognostic and diagnostic utility and the clinical management of hyperlactatemia

OBJECTIVE

To review the current literature pertaining to the use of lactate as a prognostic indicator and therapeutic guide, the utility of measuring lactate concentrations in body fluids other than blood or plasma, and the clinical management of hyperlactatemia in dogs, cats, and horses.

DATA SOURCES

Articles were retrieved without date restrictions primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Increased plasma lactate concentrations are associated with increased morbidity and mortality. In populations with high mortality, hyperlactatemia is moderately predictive in identifying nonsurvivors. Importantly, eulactatemia predicts survival better than hyperlactatemia predicts death. Consecutive lactate measurements and calculated relative measures appear to outperform single measurements. The use of lactate as a therapeutic guide has shown promising results in people but is relatively uninvestigated in veterinary species. Increased lactate concentrations in body fluids other than blood should raise the index of suspicion for septic or malignant processes. Management of hyperlactatemia should target the underlying cause.

CONCLUSION

Lactate is a valuable triage and risk stratification tool that can be used to separate patients into higher and lower risk categories. The utility of lactate concentration as a therapeutic target and the measurement of lactate in body fluids shows promise but requires further research.

The effects of lactate and acid on articular chondrocytes function: Implications for polymeric cartilage scaffold design

Poly (lactic-co-glycolic acid) (PLGA) and poly-l-lactate acid (PLLA) are biodegradable polymers widely utilized as scaffold materials for cartilage tissue engineering. Their acid degradation products have been widely recognized as being detrimental to cell function. However, the biological effects of lactate, rather than lactic acid, on chondrocytes have never been investigated. This is the major focus of this study. The amounts of lactate and the pH value (acid) of the PLGA and PLLA degradation medium were measured. The effects of PLGA and PLLA degradation medium, as well as different lactate concentrations and timing of exposure on chondrocytes proliferation and cartilage-specific matrix synthesis were investigated by various techniques including global gene expression profiling and gene knockdown experiments. It was shown that PLGA and PLLA degradation medium differentially regulated chondrocyte proliferation and matrix synthesis. Acidic pH caused by lactate inhibited chondrocyte proliferation and matrix synthesis. The effect of lactate on chondrocyte matrix synthesis was both time and dose dependent. A lactate concentration of 100mM and exposure duration of 8h significantly enhanced matrix synthesis. Lactate could also inhibit expression of cartilage matrix degradation genes in osteoarthritic chondrocytes, such as the major aggrecanase ADAMTS5, whilst promoting matrix synthesis simultaneously. Pulsed addition of lactate was shown to be more efficient in promoting COL2A1 expression. Global gene expression data and gene knock down experiments demonstrated that lactate promote matrix synthesis through up-regulation of HIF1A. These observed differential biological effects of lactate on chondrocytes would have implications for the future design of polymeric cartilage scaffolds.

STATEMENT OF SIGNIFICANCE

Lactic acid is a widely used substrate for polymers synthesis, PLGA and PLLA in particular. Although physical and biological modifications have been made on these polymers to make them be better cartilage scaffolds, little concern has been given on the biological effect of lactic acid, the main degradation product of these polymers, on chondrocytes. Our finding illustrates the differential biological function of lactate and acid on chondrocytes matrix synthesis. These results can facilitate future design of lactate polymers-based cartilage scaffolds.

Synovial IL-6 as inflammatory marker in periprosthetic joint infections

We analyzed serum and synovial biomarkers of 69 patients. 31 of them suffered from a periprosthetic joint infection (PJI) and 38 from aseptic arthralgia after total joint arthroplasty. We used Receiver-Operating-Characteristic-curves to calculate the Area-under-the-curve (AUC), cutoff-values, positive (+LR), negative (-LR) and interval-Likelihood-Ratios (iLR) for predicting a PJI. The most significant parameter was synovial interleukin-6 (IL-6) (cutoff-value ≥ 30,750 pg/ml, AUC = 0.959, SE = 90.0%, SP = 94.7%, +LR = 17.27), followed by synovial lactate (cutoff-value ≥ 8.3 mmol/l, AUC = 0.844, SE = 71.4%, SP=88.0%, +LR = 5.95), and synovial glucose (cutoff-value ≤ 44 mg/dl, AUC = 0.829, SE = 79.2%, SP = 78.6%, +LR = 3.69). IL-6 ≥ 30,750 pg/ml and lactate ≥ 10 mmol/l make a PJI very likely, IL-6 <10,000pg/ml or lactate <4.3 mmol/l makes a PJI very unlikely. If none of these thresholds are met, physicians should use the iLR of IL-6, glucose and lactate to estimate the likelihood of PJI.

Gram and acridine orange staining for diagnosis of septic arthritis in different patient populations

PURPOSE

The sensitivity of Gram staining is known to be suboptimal for the diagnosis of native joint septic arthritis. We lack information about the accuracy of Gram compared to other microscopic staining techniques for predicting infection in different patient populations.

METHODS

This was a cohort study with cost evaluations at the Orthopaedic Service of Geneva University Hospitals (January 1996-October 2012).

RESULTS

Among 500 episodes of arthritis (196 with immunosuppression, 227 with underlying arthroplasties and 69 with gout or other crystals in synovial fluid), Gram staining revealed pathogens in 146 episodes (146/500, 29 %) or in 146 of the 400 culture-positive episodes (37 %). Correlation between the Gram and acridine staining of the same sample was good (Spearman 0.85). Overall, the sensitivity, specificity, positive predictive value and negative predictive value of Gram stain for rapid diagnosis of septic arthritis was 0.37, 0.99, 0.99 and 0.28, respectively, compared to microbiological cultures. Quite similar values were recorded across the different patient subpopulations, in particular for sensitivity values that were 0.33 for patients with prosthetic joint infections, 0.40 for immunosuppressed patients, 0.36 for patients under antibiotic administration and 0.52 for patients with concomitant crystalline disease.

CONCLUSIONS

The sensitivity of Gram or acridine orange staining for a rapid diagnosis of episodes of septic arthritis is suboptimal compared to microbiological culture, regardless of underlying conditions, immunosuppression or antibiotic therapy. The sensitivity in the presence of synovial fluid crystals is moderate. Acridine orange and Gram stains are equivalent.

Analysis of synovial inflammatory markers to differ infectious from gouty arthritis

OBJECTIVES

Septic and gouty arthritis show the same clinical symptoms, but septic arthritis is an orthopedic emergency and needs immediate surgical intervention, whereas a systemic drug therapy is needed in acute gouty arthritis. The aim of this study was to investigate which inflammatory markers allow an accurate differentiation of septic and gouty arthritis.

DESIGN AND METHODS

This was a retrospective examination of serum markers (peripheral white blood cells, C-reactive Protein and uric acid) and inflammatory markers in the synovial fluid (lactate, glucose, uric acid, lactate dehydrogenase, synovial fluid white blood cell count, total protein, and interleukin-6) in 53 patients with culture-verified septic arthritis and 29 with gouty arthritis. Receiver-Operating-Characteristic-curves with corresponding Area under the curve (AUC), sensitivity, specificity, likelihood-ratio and interval likelihood-ratios were calculated to define the diagnostic potential of the inflammatory markers.

RESULTS

Synovial lactate showed the greatest diagnostic potential (AUC = 0.901, sensitivity = 89.5%, specificity = 77.3%, negative likelihood-ratio = 0.14) followed by synovial glucose (AUC=0.853) and synovial uric acid (AUC = 0.841).

CONCLUSIONS

Lactate in the synovial fluid has excellent diagnostic potential to differ septic arthritis from gouty arthritis. Synovial lactate levels above 10 mmol/L almost proofed septic arthritis, lactate levels lower than 4.3 mmol/L make it very unlikely.

Evidence-based diagnostics: adult septic arthritis

BACKGROUND

Acutely swollen or painful joints are common complaints in the emergency department (ED). Septic arthritis in adults is a challenging diagnosis, but prompt differentiation of a bacterial etiology is crucial to minimize morbidity and mortality.

OBJECTIVES

The objective was to perform a systematic review describing the diagnostic characteristics of history, physical examination, and bedside laboratory tests for nongonococcal septic arthritis. A secondary objective was to quantify test and treatment thresholds using derived estimates of sensitivity and specificity, as well as best-evidence diagnostic and treatment risks and anticipated benefits from appropriate therapy.

METHODS

Two electronic search engines (PUBMED and EMBASE) were used in conjunction with a selected bibliography and scientific abstract hand search. Inclusion criteria included adult trials of patients presenting with monoarticular complaints if they reported sufficient detail to reconstruct partial or complete 2 × 2 contingency tables for experimental diagnostic test characteristics using an acceptable criterion standard. Evidence was rated by two investigators using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS). When more than one similarly designed trial existed for a diagnostic test, meta-analysis was conducted using a random effects model. Interval likelihood ratios (LRs) were computed when possible. To illustrate one method to quantify theoretical points in the probability of disease whereby clinicians might cease testing altogether and either withhold treatment (test threshold) or initiate definitive therapy in lieu of further diagnostics (treatment threshold), an interactive spreadsheet was designed and sample calculations were provided based on research estimates of diagnostic accuracy, diagnostic risk, and therapeutic risk/benefits.

RESULTS

The prevalence of nongonococcal septic arthritis in ED patients with a single acutely painful joint is approximately 27% (95% confidence interval [CI] = 17% to 38%). With the exception of joint surgery (positive likelihood ratio [+LR] = 6.9) or skin infection overlying a prosthetic joint (+LR = 15.0), history, physical examination, and serum tests do not significantly alter posttest probability. Serum inflammatory markers such as white blood cell (WBC) counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) are not useful acutely. The interval LR for synovial white blood cell (sWBC) counts of 0 × 10(9)-25 × 10(9)/L was 0.33; for 25 × 10(9)-50 × 10(9)/L, 1.06; for 50 × 10(9)-100 × 10(9)/L, 3.59; and exceeding 100 × 10(9)/L, infinity. Synovial lactate may be useful to rule in or rule out the diagnosis of septic arthritis with a +LR ranging from 2.4 to infinity, and negative likelihood ratio (-LR) ranging from 0 to 0.46. Rapid polymerase chain reaction (PCR) of synovial fluid may identify the causative organism within 3 hours. Based on 56% sensitivity and 90% specificity for sWBC counts of >50 × 10(9)/L in conjunction with best-evidence estimates for diagnosis-related risk and treatment-related risk/benefit, the arthrocentesis test threshold is 5%, with a treatment threshold of 39%.

CONCLUSIONS

Recent joint surgery or cellulitis overlying a prosthetic hip or knee were the only findings on history or physical examination that significantly alter the probability of nongonococcal septic arthritis. Extreme values of sWBC (>50 × 10(9)/L) can increase, but not decrease, the probability of septic arthritis. Future ED-based diagnostic trials are needed to evaluate the role of clinical gestalt and the efficacy of nontraditional synovial markers such as lactate.

[Septic arthritis: practical diagnosis and new treatments]

Septic arthritis remains a major challenge to physicians because the increasing frequency of certain microorganisms to become in antibiotic-resistant and persistent difficulties regarding both early diagnostics and proper treatment of subjects with joint infections. This paper will review current diagnostics test and their contribution to the rapid evaluation of joint infection. Importantly, updated therapeutic suggestions will be presented which, when appropriately applied, should diminish the risks of sequelae following infectious arthritis.

Microbiology and management of joint and bone infections due to anaerobic bacteria

PURPOSE

To describes the microbiology, diagnosis, and management of septic arthritis and osteomyelitis due to anaerobic bacteria.

RESULTS

The predominant anaerobes in arthritis are anaerobic Gram-negative bacilli (AGNB) including the Bacteroides fragilis group, Fusobacterium spp., Peptostreptococcus spp., and Propionibacterium acnes. Infection with P. acnes is associated with a prosthetic joint, previous surgery, and trauma. B. fragilis group is associated with distant infection, Clostridium spp. with trauma, and Fusobacterium spp. with oropharyngeal infection. Most cases of anaerobic arthritis, in contrast to anaerobic osteomyelitis, involved a single isolate, and most cases are secondary to hematogenous spread. The predominant anaerobes in osteomyelitis are Bacteroides, Peptostreptococcus, Fusobacterium, and Clostridium spp. as well as P. acnes. Conditions predisposing to bone infections are vascular disease, bites, contiguous infection, peripheral neuropathy, hematogenous spread, and trauma. Pigmented Prevotella and Porphyromonas spp. are mostly isolated in skull and bite infections, members of the B. fragilis group in hand and feet infections, and Fusobacterium spp. in skull, bite, and hematogenous long bone infections. Many patients with osteomyelitis due to anaerobic bacteria have evidence of an anaerobic infection elsewhere in the body that is the source of the organisms involved in the osteomyelitis. Treatment of arthritis and osteomyelitis involving anaerobic bacteria includes symptomatic therapy, immobilization in some cases, adequate drainage of purulent material, and antibiotic therapy effective against these organisms.

CONCLUSIONS

Anaerobic bacteria can cause septic arthritis and osteomyelitis. Correct diagnosis and appropriate therapy are important contributor to successful outcome.

Management of septic arthritis: a systematic review

OBJECTIVE

To evaluate the existing evidence on the diagnosis and management of septic arthritis in native joints.

DESIGN

Systematic review.

DATA SOURCES

Cochrane Library, Medline, Embase, National Electronic Library for Health, reference lists, national experts.

REVIEW METHODS

Systematic review of the literature with evaluation of the methodological quality of the selected papers using defined criteria set out by the Clinical Effectiveness and Evaluation Unit of the Royal College of Physicians.

RESULTS

3291 citations were initially identified. Of these, 189 full text articles were identified for potential selection. Following review of these full text articles, 80 articles were found to fulfil the inclusion criteria and were included in the final list.

CONCLUSIONS

were drawn on the diagnosis, investigation and management of septic arthritis.

DISCUSSION

Little good quality evidence exists to guide the diagnosis and management of septic arthritis. Overall, no investigation is more reliable in the diagnosis of septic arthritis than the opinion of an experienced doctor. Aspiration and culture of synovial fluid is crucial to the diagnosis, but measurement of cell count is unhelpful. Antibiotics are clearly required for a prolonged period, but there are no data to indicate by which route or for how long. Key unanswered questions remain surrounding the medical and surgical management of the infected joint.

Synovial fluid analysis

AsA prompt and accurate diagnosis of a painful, swollen joint is imperative, primarily in the case of a septic joint, as delayed therapy may result in progression of disease or permanent loss of function. Procurement and analysis of synovial fluid (SF) are paramount in helping the clinician to determine a patient's clinical condition and further course of treatment. Measurement of white blood cell (WBC) counts, crystal analysis by polarized microscopy, and microbiologic studies including Gram stain and culture are the SF parameters that are collectively most important in the ultimate determination by a clinician of the presence or absence of an infectious or inflammatory joint. It is important for the clinician to understand and recognize the limitations of various SF parameters to minimize under-treating patients with potentially serious joint pathology.

Microorganisms and leukocytes in purulent sinusitis: a symbiotic relationship in metabolism

Since the exchange of gases, as well as metabolites, is greatly impeded in a paranasal sinus empyema, it is not unlikely that certain organic substances be retained and accumulated in purulent secretion. In this study, secretions aspirated from experimentally infected maxillary sinuses of 26 rabbits were analysed biochemically. Quantitatively, by far the most important acid accumulated in secretions was lactic acid. Lactate induces metabolic acidosis and exerts an inhibitory effect on mammalian defense mechanisms. Lactate may also be used as an energy source by certain microorganisms. In spite of its leukocytic origin lactic acid thus promotes the continuation of a bacterial infection. In addition, certain other organic acids of bacterial origin were found, which, in different ways, contribute to the impediment of antimicrobial defense functions.

Basic experimental studies of ostial patency and local metabolic environment of the maxillary sinus

Experimental studies of human maxillary sinus gas exchange show that there is a balance between inflow of air through the maxillary ostium and local consumption as long as the functional size of the ostium is at least 5 mm2. Maxillary sinus mucosal blood flow is 30-40 ml/100 g tissue per minute, as measured in plethysmographic studies. This blood flow can bind and transport only half of the absorbed oxygen, the rest is consumed. Experimental histo- and biochemical studies of sinusitis show anaerobic mucosal metabolism with shortage of energy supply due to inadequate oxygen supply. There is no decrease in oxidative enzyme capacity of the mucosal epithelium. Analysis of organic acids in purulent secretion indicates that the high lactate and CO2 concentration found is mainly the result of leucocyte glycolysis with local lactic acidosis. Both ostial occlusion and the initiation of bacterial growth in serous sinusitis may be secondary to an initial inflammatory response, resulting in local tissue pathology and swelling of the ostiomeatal complex, as well as creating the appropriate redox potential for further bacterial growth in the secretions.

The effects of lactic acid on PGE2 production by macrophages and human synovial fibroblasts: a possible explanation for problems associated with the degradation of poly(lactide) implants?

The aim of this study was to investigate the effects of lactic acid on cells found at the bone-implant interface in order to try to discover more about the effects of degradation of implants manufactured from poly(lactide). This study shows that human synovial fibroblasts and murine macrophages release prostaglandin E2 (PGE2) a bone resorbing and inflammatory mediator, into the surrounding medium when exposed to lactic acid. The production of PGE2 in response to lactate may help to explain isolated cases of inflammation and discomfort seen some time after fracture fixation with poly(lactide) implants.

Sequential clinical and synovial fluid changes associated with acute infectious arthritis in the horse

Infectious arthritis was induced experimentally in one tarsocrural joint of six horses by intra-articular injection of 1 ml Staphylococcus-saline suspension containing 9 x 10(4) to 3 x 10(6) organisms. The corresponding contralateral joint was injected with 1 ml of saline and served as a control. The progression of the induced infectious arthritis was assessed over a nine-day period by clinical examination and sequential synovial fluid analysis with pH and lactate measurements. Changes in synovial fluid were present before clinical signs of infectious arthritis were manifested. The diagnostic value of different synovial fluid parameters at various stages of infection was determined. Cellular changes initially preceded the biochemical changes. Total leucocyte counts showed a significant increase within 24 h (up to 100 x 10(9)/litre) with great variability in subsequent measurements. Neutrophilia over 90 per cent and pH under 6.9 were the most consistent findings in the infected synovia. Increased total protein was also significant and was progressive throughout the experiment. Serum and synovial glucose difference and synovial lactate had more diagnostic value in the acute stages than in the chronic stages. The control joints elicited an inflammatory response manifested by increased leucocyte count, moderate neutrophilia, slightly increased total protein concentration, and slightly decreased pH, but all reactions were minor in comparison to those in the infected joints.

The influence of corticosteroids on sequential clinical and synovial fluid parameters in joints with acute infectious arthritis in the horse

Infectious arthritis was induced experimentally in one tarsocrural joint of six horses by intra-articular injection of 1 ml Staphylococcus aureus-saline suspension with the addition of 200 mg methylprednisolone acetate. The corresponding contralateral joint was injected with 1 ml of saline with the addition of 200 mg methylprednisolone acetate, and served as a control. The purpose of the experiment was to examine the effect of corticosteroids on the acute clinical signs of infectious arthritis, and the associated changes in synovial fluid, to separate the effects of a steroid injection from those of infection alone. This should aid early diagnosis of infection. The progression of the infectious arthritis was assessed over nine days by clinical examination and sequential synovial fluid analysis. The corticosteroids masked the clinical signs in some horses for up to the third day although changes in the synovial fluid were present earlier. Cellular changes preceded biochemical changes initially. Leucocyte counts showed a significant increase in cell numbers after infection was established. Persistent neutrophilia, over 90 per cent, together with a pH under 6.9 were the most consistent findings in the infected synovia. Total protein values were lower in infected joints with, than those without, corticosteroids; although there was a progressive rise in total protein concentration throughout the experiment in both groups. Serum and synovial glucose difference and synovial lactate had very little diagnostic value because significant increases due to the corticosteroids were documented in the control joints.

Synovial fluid lactic acid in acute and chronic pyrophosphate arthropathy and in osteoarthritis

A comparison of synovial fluid lactate levels has been made in cases of chronic pyrophosphate arthropathy (PA) with and without joint destruction, acute PA and osteoarthritis. No statistically significant difference could be observed between results of chronic PA and osteoarthritis. By contrast, synovial fluid lactate levels were significantly higher in acute PA in comparison with the two other groups. These data suggest that hypoxia is unlikely to play a role in destructive arthropathy commonly found in chronic PA.

Bacterial arthritis in an English health district: a 10 year review

Bacterial arthritis continues to present a difficult clinical and therapeutic problem, necessitating prompt diagnosis and intensive therapy. This study comprises a 10 year review of the condition in an English health district, with particular reference to aetiology, presentation, treatment, and outcome. Although the causative organisms remain qualitatively unchanged, increasing numbers of patients are elderly, immunosuppressed, or have underlying arthropathy. Factors which influence outcome include age, causative organism, joint involved, and delay in diagnosis. Attention is drawn to the notably poor outcome of hip infections in the elderly.

Septic arthritis. Clinical approach to the 'hot joint'

Joint space infections continue to be among the most common forms of arthritis. Diagnosis can be difficult, particularly in the presence of underlying joint disease. Septic arthritis should be suspected in all patients who present with an acutely swollen joint. Immediate joint aspiration with Gram's stain and culture of the synovial fluid is essential. Intensive, long-term antibiotic therapy is necessary to prevent a high rate of morbidity and, possibly, death.

Prepatellar bursitis in wrestlers

As part of a larger retrospective study examining all knee injuries sustained by the University of Iowa wrestling team over 6 years, prepatellar bursitis was found to be the most frequent injury and, therefore, was examined in depth. Of the 136 wrestlers studied, 13 developed an initial case of prepatellar bursitis. This represented 21% of all initial episodes of knee injuries. Five of these wrestlers had no recurrences, but the other eight together had 20 recurrences. Median time lost for the initial injury was only 4 days, but recurrences and surgeries added significantly to the total time lost. There were only two cases of septic prepatellar bursitis, but there have been six cases (in four wrestlers) in the three seasons since the end of the larger study period. The infecting organism in all but one case was Staphylococcus aureus and was penicillin-resistant in all but one. There was no clinical evidence of infection in 50% of the cases, emphasizing the need to do a Gram's stain and culture (and, therefore, an aspiration) on all cases of prepatellar bursitis. The prognosis appeared better if the wrestler had no previous history of bursitis, suggesting that pathologic changes in the bursal wall may impair its defense mechanisms. In sharp contrast to all other knee injuries, most prepatellar bursitis cases occurred in the off-season. Most developed insidiously, but direct impact during a takedown maneuver is suspected as being the most frequent cause.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic significance of pleural fluid lactate concentrations

Lactate concentrations in the pleural fluid and plasma of 57 patients with pleural effusions were measured by an enzymatic method. The mean pleural fluid lactate concentrations were significantly higher in patients with empyemas and rheumatoid arthritis than in patients with tuberculosis, cancer, non-specific pleural effusions and congestive heart failure. Pleural fluid lactate concentrations correlated significantly with pleural fluid lactate dehydrogenase activities and inversely with pleural fluid glucose concentrations. An elevated pleural fluid lactate concentration is not diagnostic for empyema, as most patients with rheumatoid arthritis and some with tuberculosis and cancer also show high values.

Synovial fluid lactate levels in septic and non-septic arthritides

Lactate concentration was studied in 383 synovial fluid specimens from patients with various arthritides. The highest concentrations of lactate occurred in non-gonococcal septic synovial fluids. High values were recorded in seropositive rheumatoid arthritis and crystal-induced arthritides, medium values in synovial fluids from seronegative rheumatoid arthritis, seronegative spondylarthritides, gonococcal arthritis and haemarthrosis, and the lowest values in aspirates from osteoarthrotic joints. There was a positive correlation between synovial pH and lactic acid concentration. These data suggest that determination of lactate in synovial fluid can be valuable in the rapid exclusion of septic arthritis. Its value for differentiating between other inflammatory arthritides is discussed.

Value of pleural lactate in the differential diagnosis between empyema and non-bacterial pleural effusions

Lactate concentrations in the pleural fluid of 50 patients were determined by the Monotest Lactate Kit. Lactate values were found higher in bacterial pleural infections than in cases of hydrothorax. Elevated levels were also found in most cases of histologically confirmed cases of pleural neoplasms and in some cases of non-bacterial pleuritis exsudativa . The highest levels were found in cases of empyema, but there was considerable overlapping between the groups. Pleural lactate thus appears to have little diagnostic value in the differential diagnosis between empyema and non-bacterial pleural effusions.

Lactate levels in Brucella arthritis

In this study the synovial fluid cell types and the synovial fluid lactate levels of patients with Brucella, septic rheumatoid, gouty and osteoarthritic mono-arthritis are presented. It is shown that lactate levels coupled with the clinical picture and the cell type of the synovial fluid appear to be an early additional diagnostic marker for the differentiation between septic, inflammatory and brucella-induced mono-arthritis.

Clinical utility of lactic acid measurement in body fluids other than plasma

The diagnosis of septic infections of closed body cavities requires a careful search. Traditional laboratory tests such as Gram's stain, white cell count, and protein and glucose levels are often inconclusive. Measurement of lactic acid in cerebrospinal, synovial, pleural, ascitic, and bursal fluids has been utilized to distinguish bacterial from nonbacterial infections. The present review summarizes the current status of lactic acid measurement in the differential diagnosis of meningitis, arthritis, empyema, bacterial peritonitis, and bursitis.

Synovial fluid lactic acid in septic and nonseptic arthritis

We determined lactic acid levels by the lactic dehydrogenase method in synovial fluid of 41 patients with various rheumatic diseases, to test the concept that significantly elevated values were diagnostic of septic arthritis. Nine patients had septic arthritis, 15 rheumatoid arthritis (RA), and the remainder miscellaneous conditions. In another 9 patients with different rheumatic diseases, including 1 with septic arthritis, synovial fluid lactic acid was determined by both the lactic dehydrogenase and gas-liquid chromatography methods. There was a wide scatter of values among patients with septic and nonseptic inflammatory arthritis, and much overlap occurred. We could not differentiate septic arthritis from RA on the basis of synovial fluid lactic acid levels. Results were similar with both procedures for determining lactic acid levels.

Gas-liquid chromatographic analysis of synovial fluid: volatile short-chain fatty acids in septic arthritis

Volatile short-chain fatty acids (SCFA) in synovial fluid from 80 patients were quantified by gas-liquid chromatography (GLC). Characteristic patterns of volatile SCFA could not be associated with septic, nonseptic inflammatory, or noninflammatory groups. Mean concentrations of pentanoic and hexanoic acids were similar in all groups studied. In the septic arthritis group 3 of 4 patients with acetic acid and of 3 of 3 with 3-methyl butanoic acid had culture-proved staphylococcal infections. In patients with synovial fluid findings consistent with septic arthritis, including markedly raised leucocyte count, decreased glucose level, or detectable succinic acid, the detection of acetic and 3-methyl butanoic acids by GLC analysis may increase the suspicion that Staphylococcus aureus is the cause of the septic arthritis.

Gas-liquid chromatographic analysis of synovial fluid. Succinic acid and lactic acid as markers for septic arthritis

Nonvolatile short-chain fatty acids from 80 synovial fluids were quantified by gas-liquid chromatography. Succinic acid was detectable in all 23 septic synovial fluids infected with either gram-positive or gram-negative organisms and in only 5 of 57 nonseptic synovial fluids. Lactic acid was present in all of the effusions but was correlated with septic arthritis only when present in concentrations greater than 250 mg%. Neither short-chain fatty acid was more sensitive than high white blood cell counts (greater than 50,000 mm3) or depressed glucose concentration (less than 40 mg/dl) in diagnosing septic arthritis before antibiotic therapy; however, the detection of succinic acid was helpful in identifying patients with septic arthritis who had been given antibiotic treatment before arthrocentesis. Thus, gas-liquid chromatography, a rapid and sensitive method for the detection of short-chain fatty acids, may complement the currently available methods used to diagnose septic arthritis.

Synovial fluid lactic acid measurement in the diagnosis and management of septic arthritis

An improved method of lactic acid estimation by gas liquid chromatography (GLC) is described. Synovial fluid lactic acid estimation was performed on 52 patients (15 with septic arthritis and 37 with non-septic arthropathies) and compared to routine microbiological methods and white cell counts. Lactic acid was found to be a useful and rapid test for differentiating between septic and non-septic arthritis being markedly raised (greater than 12 mmol/l) in all the septic joints. Raised lactic acid concentrations were of particular diagnostic value in patients in whom antibiotic therapy had commenced before joint aspiration. The results of lactic acid estimation on sequential samples were helpful in assessing the response of septic arthritis to treatment.

Measurement of lactate in ascitic fluid: an aid in the diagnosis of peritonitis with particular relevance to spontaneous bacterial peritonitis of the cirrhotic

Lactate concentrations were measured in the ascitic fluid of patients using the Monotest Lactate Kit, an inexpensive, reliable bedside test that gives results within 15 min. The values were significantly higher in 24 patients with proven bacterial peritonitis, eight of them with spontaneous bacterial peritonitis, than in 53 patients with uninfected ascites of various other etiologies. In only two patients from the latter group, both with hepatic carcinoma and peritoneal metastases, were the values in the range found in bacterial peritonitis. Lactate determination was at least as sensitive as measurement of WBC levels for diagnosing peritonitis. Serial determinations in two patients with peritonitis showed declining values as the disease responded to treatment. The test has particular relevance for patients with spontaneous bacterial peritonitis, because this disease, which is potentially life-threatening although frequently asymptomatic, requires immediate treatment, yet currently depends on time-consuming culture procedures for diagnosis.

Lactate UV-system: a rapid method for diagnosis of septic arthritis

The concentration of lactic acid in synovial fluid was estimated in 43 specimens from patients with an acute monoarthritis by a simple enzyme method. In 9 patients with 10 episodes of septic arthritis concentrations of synovial fluid lactic acid were significantly higher (mean 10.8 mmol/l) than in 33 patients with nonseptic effusions (mean 3.1 mmol/l). With this method concentrations of synovial fluid lactic acid provide a rapid diagnostic guide in the separation of septic from nonseptic arthritis.

Synovial fluid lactate determinations as a diagnostic aid in cases of monoarticular arthritis

The concentration of synovial fluid lactate was determined by an enzymatic kit method in 16 patients with various types of monoarticular arthritis and in 2 patients with non-inflammatory lesions and no joint effusion. Lactate concentrations in control cases were 1.2 mmol/l, in septic arthritis above 10 mmol/l, in pseudogout and yersinia arthritis around 7 mmol/l, and in other cases of inflammatory, nonseptic arthritis around 3.0 mmol/l.