An update on recent progress of the epidemiology, etiology, diagnosis, and treatment of acute septic arthritis: a review

Identifying septic arthritis superimposed on crystalline arthropathy: Is synovial cell count the answer?

Background

Septic arthritis (SA) is an orthopedic urgency with significant morbidity and potential mortality. Differentiating SA and crystalline arthritis (CA) is difficult as concurrent disease may exist. This study sought to identify the prevalence of and define diagnostic laboratory markers for SA in the setting of CA.

Methods

A retrospective review was conducted of adult patients presenting to a single medical center between January 2012 and March 2023 with monosodium urate (MU) or calcium pyrophosphate (CPP) in synovial knee joint fluid of a native knee. Categorical variables were assessed using chi-square and Fisher exact tests. Receiver operating characteristic curves were computed, and diagnostic accuracy was determined from associated area under the ROC curve (AUC). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated and optimal diagnostic thresholds determined by Youden index.

Results

225 knee aspirations were analyzed, 56.4 % CPP and 43.6 % MSU. There were 12 cases of superimposed SA (5.3 %), 11 culture confirmed and 1 suspected. Immunosuppression was associated with a higher incidence of SA (41.7 % versus 14.6 %, p = 0.0271). SA had a significantly higher mean synovial WBC (135,796 vs 22,510; p = 0.0007). There was no difference in percentage of PMNs between the septic and aseptic groups (90.6 % vs 69.7 %; p = 3.327). Of the 12 cases of concomitant SA, 10 (83.3 %) had a synovial WBC ≥50,000/mm3, compared to 21 (9.9 %) of the aseptic aspirations (p < 0.0001). Nine (75 %) aspirations in the septic group had ≥90 % PMNs, compared to 78 (36.6 %) in the aseptic group (p = 0.0123). The optimal diagnostic threshold for synovial WBC was 50,000/mm3 (91.7 % sensitivity, 90.1 % specificity, AUC = 0.960). The optimal synovial percentage of PMNs was 64 % (100 % sensitivity, 6.7 % specificity, AUC = 0.731).

Conclusion

In the setting of CA, synovial WBC may provide a useful diagnostic marker for SA with an optimal threshold of 50,000 cells/mm3.

Detection of bacterial pathogens directly from synovial fluids using digital PCR: A proof of concept study

Diagnosis of joint infections is often challenging due to low specimen volumes, low sensitivity of Gram stains and long incubation times of cultures. Digital PCR (dPCR) is a molecular tool that can detect nucleic acid targets with high sensitivity and resistance to inhibition. A 3 hour dPCR assay targeting the 16S gene was performed on archived synovial fluids. The assay detected the 16S gene directly from 4 µL of joint fluid without nucleic acid extraction. In 43 culture positive neat synovial fluids, the dPCR instrument detected 31 (72%) as positive, and 12 (28%) as indeterminate. In 49 culture negative specimens, dPCR was negative for 34 (69%), indeterminate for 14 (29%). The detection of bacteria was similar to real-time PCR performed on extracted specimens and demonstrated superior sensitivity to Gram stain. This technique shows potential as a rapid detection method for bacterial pathogens in synovial fluids, with optimization to improve specificity.

Septic arthritis - symptoms, diagnosis and new therapy

Septic arthritis (SA) is an infection of one or more joints caused mainly by Staphylococcus aureus, to a lesser extent by streptococci and Gram-negative bacilli. It poses a huge medical problem due to its high mortality rate of 2-15%. Disease symptoms are often vague, resulting in a risk that SA may be diagnosed too late. This shows the urgency of finding a rapid diagnostic method for SA and an effective therapy. Basic treatment of SA including joint drain or empirical antimicrobial therapy does not always provide the desired results. Hence, new therapies are being sought, including the use of antimicrobial peptide or phage therapy.

Eikenella corrodens in a patient with septic arthritis: A case report

Eikenella corrodens, a Gram-negative bacterium, is typically associated with fight-bite injuries and, in rare cases, with infective endocarditis. Infection may arise either through direct inoculation or through invasion of oral mucosa with subsequent bacteraemia. This bacterium is an unusual cause of infection in immunocompetent patients without direct injury. There are no studies published from Ethiopia on identification of Eikenella corrodens in humans. In this case report, we describe a patient with a septic arthritis and tibia bone abscess where Eikenella corrodens was identified. Recognition of septic arthritis was delayed and identification of the microorganism was challenging. This influenced the choice and duration of treatment and has likely affected the patient's outcome. This case report emphasizes the significance of recognizing rare pathogens in complex cases, considering slow-growing microorganisms and anticipating treatment challenges when uncommon microorganisms are involved.

Septic Arthritis: Current Concepts

Septic arthritis is a major cause of morbidity and mortality worldwide, with survivors often facing long-term functional impairments. Prompt diagnosis is crucial to decrease complications such as cartilage loss, osteomyelitis, and reduced mobility. Imaging plays a central role in the diagnosis, as well as offering guidance for diagnostic aspiration. Because septic arthritis may involve any joint in the body, both native and prosthetic, different imaging modalities may be more applicable in various scenarios. We describe the hallmark imaging findings of septic arthritis in radiography, ultrasound, computed tomography, magnetic resonance imaging, and nuclear medicine scintigraphy, as well as the associated complications.

Bilateral Septic Arthritis of the Wrist With Streptococcus dysgalactiae: A Case Report

CASE

Septic arthritis is an infection of the joint space that can lead to joint destruction, disability, and death. Mortality risk is increased by old age, comorbidities such as decreased kidney function, and involvement of multiple joints. We report a rare case of bilateral septic arthritis of the wrists in a 101-year-old woman who recovered without complications.

CONCLUSION

This case illustrates the necessity of monitoring pain in other joints in cases of monoarticular septic arthritis to rule out polyarticular involvement to prevent long-term complications, morbidity, and mortality.

Low Prevalence of Anaerobic Bacteria in Pediatric Septic Arthritis Makes Obtaining Anaerobic Cultures of Questionable Value

BACKGROUND

Pediatric acute septic arthritis necessitates urgent identification and treatment to avoid irreversible joint damage if not recognized and treated in a timely manner. Many centers routinely obtain both aerobic and anaerobic cultures for the purpose of pathogen identification; however, the yield of anaerobic culture results has been called into question. The goal of this study was to determine the positivity rate of anaerobic cultures collected intraoperatively in pediatric patients with clinically diagnosed septic arthritis.

METHODS

Patients with a clinical diagnosis of septic arthritis were extracted from a search of musculoskeletal infections at a large tertiary care pediatric hospital from 2007 to 2021. Cultures obtained from the operating room or through arthrocentesis were examined.

RESULTS

We identified 470 cases of pediatric septic arthritis of which only 3 cultures were positive (0.6%) for anaerobic organisms. All cases involved a single isolate. The anaerobic bacteria that were detected included 1 facultative anaerobe, 1 strict anaerobe, and 1 relatively aerotolerant anaerobe. Four aerobic organisms grew on the anaerobic cultures. Three of the false positives also grew on aerobic culture media, whereas 1 aerobic specimen grew explicitly on anaerobic media. Neither the facultative anaerobe nor the aerotolerant anaerobe grew on aerobic culture media.

CONCLUSIONS

Over a 14-year period, only 0.6% (3 cases) of septic arthritis cases yielded positive anaerobic cultures that were not able to be cultured on aerobic media. As such, an anaerobic culture was more likely to culture a bacterium that would have also been cultured on aerobic media. In addition, a true positive anaerobic culture that would not have been diagnosed on aerobic cultures only occurs about once every 5 years at our institution. If one were to decide against obtaining anaerobic cultures, they would only miss 3 infections out of almost 500 (0.6%), and antibiotics would only have changed 0.6% of the time. These results suggest that routinely obtaining anaerobic cultures may be of limited value in pediatric septic arthritis. The false-positive rate of anaerobic labs exceeds that of true-positive cases. These results provide actionable opportunity to help guide clinician decision-making in a more cost-effective and efficient management of pediatric septic arthritis.

LEVEL OF EVIDENCE

IV.

In situ dual-targeted drug delivery system for alleviating imaging and pathological damage in septic arthritis

Septic arthritis is a severe disease that damages articular cartilage and triggers a strong inflammatory response. Current treatments mainly depend on systemic antibiotics and lack effective intra-articular therapies, as well as standardized animal models, and precise detection methods. In this study, we present a drug delivery system responsive to the bacterial microenvironment for targeted inflammation control, along with an effective method for monitoring changes in septic arthritis in SD rats. This system consists a core with pH-sensitive metal-organic frameworks ZIF-8 loading anti-inflammatory drugs indomethacin and a shell with hybrid cell membranes from macrophages (MM) and platelets (PM), refer as MP@ZIF-8@IN. This system, which diverges from traditional treatments, enhances drug utilization, prolongs local retention, and allows for spontaneous release at the treatment site, thereby enabling the exclusive intra-articular treatment of septic arthritis. The drug delivery system inhibits the NF-κB pathway, reduces oxidative stress, and regulates macrophage polarization, preventing cartilage destruction. Additionally, in this standardized animal model utilizing the knee joints of SD rats, we have developed musculoskeletal ultrasound and magnetic resonance imaging for time-based monitoring, thus overcoming the limitation of conventional methods, which are unsuitable for soft tissue analysis. Our findings advance therapeutic strategies for septic arthritis and encourage further application of visualization techniques in related fields. STATEMENT OF SIGNIFICANCE: This study presents significant advancements in the treatment and understanding of septic arthritis. Our customized drug delivery system targets bacteria and macrophages, ensuring long-time drug retention and enhanced inflammation control, all while reducing reliance on antibiotics-an important step toward addressing antibiotic resistance. Additionally, we have refined septic arthritis animal models to establish clearer guidelines for intervention timing, grounded in clinical symptoms and imaging data. This addresses a critical gap in current research and offers a practical framework for future therapeutic approaches.

18F-FDG PET/CT for the diagnosis of septic shoulder arthritis: metabolic uptake pattern and diagnostic performance

BACKGROUND

Septic arthritis (SA), although rare, is a critical joint-threatening emergency. The shoulder, being the third most common site after knee and hip joints, is predominantly affected by hematogenous spread of infection. 2-deoxy-2-[18F]fluoro-D-glucose (F-18-FDG) positron emission tomography (PET)/computed tomography (CT) has shown promise in identifying infectious foci and modifying treatment plans. This study aims to differentiate the metabolic patterns of septic shoulder arthritis (SSA) from various stages of shoulder osteoarthritis (OA) using F-18-FDG PET/CT and assess its diagnostic performance.

METHODS

We retrospectively included subsequent patients diagnosed with SSA between November 2017 and October 2023, who had undergone whole-body F-18-FDG PET/CT scans within 2 weeks before and after diagnosis. The control group included noninfected contralateral shoulder joints and patients who underwent F-18-FDG PET/CT for malignant melanoma staging without evidence of acute infections. Visual and quantitative analyses of F-18-FDG uptake, measured as maximum standardized uptake value (SUVmax), were conducted. OA severity was categorized using the Kellgren and Lawrence system. To establish a cut-off for SSA, a ratio of joint uptake to liver uptake of 18F-FDG was calculated using the SUVmax of the shoulder joint and liver. Intraobserver and interobserver reliability were assessed through repeated measurements.

RESULTS

Of 150 shoulders, 149 were included in the study: 13 into the experimental group with confirmed SA and 136 into the control group. One shoulder was excluded from the control group due to metastasis. Thirteen shoulders had confirmed SA. In the control group, F-18-FDG uptake measured by SUVmax increased significantly with OA severity (P = .001). SSA exhibited markedly higher F-18-FDG uptake compared to controls (P < .001). Visual intensity assessments corroborated these findings (P < .001). For a cut-off value of 1 for the joint-liver-ratio, sensitivity, specificity, positive predictive value, and negative predictive value for distinguishing between SSA and OA were 92.3%, 80.9%, 31.6%, and 99.1%, respectively. Interobserver and intraobserver reliability were moderate to high. The intraclass correlation coefficients for standardized uptake value measurements in the total shoulder were 0.994 and 0.996, respectively, while Cohen's kappa coefficients for visual analysis were 0.570 and 0.891.

CONCLUSION

F-18-FDG PET/CT effectively differentiates SSA from varying stages of OA. The SUVmax in liver can be used as a cut-off value with high sensitivity and specificity. A negative F-18-FDG PET/CT excludes SSA.

Staphylococcus aureus in Inflammation and Pain: Update on Pathologic Mechanisms

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium of significant clinical importance, known for its versatility and ability to cause a wide array of infections, such as osteoarticular, pulmonary, cardiovascular, device-related, and hospital-acquired infections. This review describes the most recent evidence of the pathogenic potential of S. aureus, which is commonly part of the human microbiota but can lead to severe infections. The prevalence of pathogenic S. aureus in hospital and community settings contributes to substantial morbidity and mortality, particularly in individuals with compromised immune systems. The immunopathogenesis of S. aureus infections involves intricate interactions with the host immune and non-immune cells, characterized by various virulence factors that facilitate adherence, invasion, and evasion of the host's defenses. This review highlights the complexity of S. aureus infections, ranging from mild to life-threatening conditions, and underscores the growing public health concern posed by multidrug-resistant strains, including methicillin-resistant S. aureus (MRSA). This article aims to provide an updated perspective on S. aureus-related infections, highlighting the main diseases linked to this pathogen, how the different cell types, virulence factors, and signaling molecules are involved in the immunopathogenesis, and the future perspectives to overcome the current challenges to treat the affected individuals.

Lidocaine Shows Significant Antimicrobial Effects Against Staphylococcus Species: An In-Vitro Study Comparing Different Combinations of Lidocaine and Clinically Used Injectables, like Steroids and Hyaluronan, in the Context of Arthritis Management

INTRODUCTION

Intra-articular injections, commonly used in osteoarthritis treatment, are debated due to their potential link to septic arthritis, though its incidence remains low. Lidocaine, used as a "carrier" for therapeutic substances like hyaluronan or triamcinolone, has pain-relieving and antimicrobial properties. This study investigates the concentration-dependent antimicrobial effects of lidocaine in combination with hyaluronan and triamcinolone in both standard and synovial fluid cultures.

METHODS

The antimicrobial efficacy of lidocaine against Staphylococcus aureus was investigated, with variations in bacterial and lidocaine concentrations. Bacterial growth was monitored using a UV/VIS spectrometer at 600 nm. Lidocaine solutions of 1% and 2% were tested, both alone and in combination with hyaluronic acid or Triam40, in tryptic soy broth (TSB), to reflect knee joint applications. The groups included pure lidocaine (L), Triam (T), hyaluronan (H), and combinations (LT, LH, TH, LTH) with 1% or 2% lidocaine. A bacterial inoculum of 300 CFU/mL was used, and samples were incubated for 12 and 24 h. Additional tests were conducted on Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus (MRSA), as well as on S. aureus in human synovial fluid.

RESULTS

Lidocaine showed a concentration-dependent antimicrobial effect, with greater inhibition at higher concentrations and lower bacterial densities. All lidocaine-containing combinations significantly reduced the bacterial levels of S. aureus in TSB. Similar results were seen for S. epidermidis and MRSA, with notable inhibition in synovial fluid after 12 h, especially with 2% lidocaine.

CONCLUSIONS

Lidocaine exhibits dose-dependent antimicrobial effects against key pathogens responsible for septic arthritis. Its combination with Triam40 and hyaluronan may reduce the risk of septic arthritis, supporting its clinical relevance.

Genetic Testing Technology Assisting in the Diagnosis and Treatment of Multiple Suppurative Arthritis and Extensive Migratory Skin and Soft Tissue Infections Caused by Disseminated Staphylococcus aureus Disease: A Case Report and Review

Staphylococcus aureus (S. aureus) infection is readily disseminated, yet the multiple septic arthritis and extensive migratory skin and soft tissue infections it causes are uncommon and challenging to treat. The infection can be life-threatening, with a mortality rate of 15-31%. Early, targeted antibiotic therapy is critical to improve prognosis. However, routine cultures are time-consuming and have low positivity rates, which may lead to errors in antibiotic regimen selection, depriving patients of optimal treatment. Genetic testing technologies, such as macrogenomic next-generation sequencing (mNGS) and digital polymerase chain reaction (dPCR), are now emerging as powerful tools for early pathogen diagnosis as well as pathogen diagnosis of target detectors with low microbial loads. In this study, we report a 53-year-old man who was admitted to the ICU for treatment of septic shock. The causative agent was targeted earlier as S. aureus by mNGS, and the shock was corrected more quickly with targeted antibiotic medication. However, he later developed multiple septic arthritis and an extensive migratory skin soft tissue infection with persistent fever, and at one point a gram-negative bacterial infection was suspected, and the antibiotic regimen was incorrectly changed. Blood dPCR suggested that the causative organism was still methicillin-sensitive S. aureus (MSSA), with no drug resistance gene detected, and the anti-infective regimen was readjusted, and the patient eventually recovered and was discharged from the hospital. We present this rare case and review related studies to validate the superiority of genetic testing technology in pathogen diagnosis, which deserves further application.

Native and prosthetic septic arthritis in a university hospital in Saudi Arabia: A retrospective study

BACKGROUND

Septic arthritis, whether native or prosthetic, poses a significant challenge in clinical practice due to its potentially devastating consequences. Despite its clinical importance, there remains a dearth of comprehensive studies and standardized diagnostic criteria, particularly in the Kingdom of Saudi Arabia.

AIM

To investigate the epidemiology, microbiological profiles, and clinical characteristics of native and prosthetic septic joints in the Saudi Arabian population.

METHODS

Medical records of patients diagnosed with septic arthritis between January 1, 2015, and December 31, 2022, were retrospectively reviewed. Data regarding patient demographics, clinical presentation, microbiological cultures, treatment modalities, and outcomes were analyzed.

RESULTS

In a retrospective review of 52 cases of septic arthritis, a balanced gender distribution was observed (1:1 ratio), with the knee being the most commonly affected joint (80.8%). Methicillin-resistant Staphylococcus aureus predominated in native joints (24.2%), while Brucella spp. was more prevalent in prosthetic joints (21.1%). Joint preservation was achieved in most cases (84.6%), with no significant difference in clinical features between native and prosthetic joints. However, certain comorbidities were more common in native joint cases, including renal impairment (P = 0.002), hemodialysis (P = 0.004), heart disease (P = 0.013), and chronic liver disease (P = 0.048). At the same time, osteoarthritis was more prevalent in prosthetic joint cases (P = 0.013). Vancomycin was the most frequently used antibiotic (26.9%), and most patients received antibiotics before joint aspiration (57.7%). Surgical intervention, predominantly arthrotomy, was required in most cases (32.7%). Notably, a significant association was found between joint type and mortality (odds ratio = 0.587, P = 0.048), as well as the Charlson comorbidity index and mortality (P = 0.001).

CONCLUSION

This study highlighted distinctive microbiological profiles and etiological factors in septic arthritis cases in the Saudi Arabian population.

Predictive value of joint fluid volume on advanced pre-procedure imaging related to success of arthrocentesis and presence of septic arthritis

PURPOSE

Septic arthritis is a dangerous medical condition requiring prompt diagnosis, often via arthrocentesis. A "dry tap" occurs when no fluid is aspirated. We hypothesized that the absence of a joint effusion on pre-procedure advanced imaging would reliably predict a dry tap and exclude septic arthritis.

METHODS

A cohort of 217 arthrocentesis cases of large joints (hips, shoulders, knees) from our institution, with pre-procedure advanced imaging (CT, MR, US) of the same joint performed within the previous 48 h, was analyzed. Exclusion criteria included non-native joints or inadequate imaging of the affected joint. These cases underwent blinded review by 4 radiologists who measured the deepest pocket of joint fluid on the pre-procedure imaging. Wilcoxon rank-sum test was performed comparing joint fluid pocket size to outcomes of successful aspiration and final diagnosis.

RESULTS

A smaller average joint pocket fluid size was present on advanced imaging in both dry taps compared with successful arthrocenteses (p < .0001), and in uninfected joints compared with septic joints (p = .0001). However, the overlap of values was too great to allow for a perfectly predictive cutoff. 29% (5/17) of patients with no visible joint fluid on pre-aspiration imaging underwent successful arthrocentesis, one case representing septic arthritis.

CONCLUSION

Volume of joint fluid on advanced pre-arthrocentesis imaging cannot reliably predict subsequent dry tap nor exclude septic arthritis.

Arthroscopy or arthrotomy for native knee septic arthritis: A systematic review

Purpose

Septic arthritis of any joint is an orthopaedic emergency which requires prompt diagnosis and treatment. The knee is the commonest joint afflicted, and the primary objective of any treatment is complete source control. This commonly takes the form of antibiotic therapy and a washout of the infected joint by means of arthroscopy or arthrotomy. The primary aim of this review is to investigate if arthroscopic washout for native knee septic arthritis confers a lower risk of repeat procedure than arthrotomy.

Methods

A systematic review and meta-analysis was conducted of the MEDLINE, SCOPUS and the Cochrane Library data bases. The primary outcome of interest was requirement for repeat washout with all-cause complications, length of inpatient stay and mortality secondary outcomes.

Results

A total of 17,140 subjects were included for analysis of the primary outcome, and the overall rate of repeat procedure was 14.6%. No statistical difference was found between arthroscopy and arthrotomy for repeat washout (risk ratio 0.86 [95% confidence interval, CI: 0.72-1.02], I 2 = 36%). Eligible studies found in favour of arthroscopy for all-cause complication rate (risk ratio 0.75 [95% CI: 0.6-0.93], I 2 = 84%) and length of stay in hospital (mean difference -1.98 days [95% CI: -3.43 to -0.53], I 2 = 84%). No statistical difference was found for the mortality rate (risk ratio 1.17 [95% CI: 0.52-2.63], I 2 = 57%).

Conclusion

Our analysis found arthroscopy and open arthrotomy to be equivocal for repeat surgical washout in native knee septic arthritis. All-cause complication rate and length of inpatient stay were favourable for arthroscopy with no difference noted between mortality rates.

Level of Evidence

Level III.

Current updates in MSK infection imaging: A narrative review

This article presents a comprehensive overview of the diagnostic utility of existing imaging techniques including radiography, computed tomography, ultrasonography, magnetic resonance imaging (MRI), and radionuclide imaging in the context of the most common orthopaedic or musculoskeletal infections. It also includes illustrative images showcasing significant findings in various musculoskeletal infections including osteomyelitis, cellulitis, septic arthritis, necrotising infections and peri-prosthetic joint infections and their associated complications.

Potential value of a rapid syndromic multiplex PCR for the diagnosis of native and prosthetic joint infections: a real-world evidence study

Introduction: The BIOFIRE Joint Infection (JI) Panel is a diagnostic tool that uses multiplex-PCR testing to detect microorganisms in synovial fluid specimens from patients suspected of having septic arthritis (SA) on native joints or prosthetic joint infections (PJIs). Methods: A study was conducted across 34 clinical sites in 19 European and Middle Eastern countries from March 2021 to June 2022 to assess the effectiveness of the BIOFIRE JI Panel. Results: A total of 1527 samples were collected from patients suspected of SA or PJI, with an overall agreement of 88.4 % and 85 % respectively between the JI Panel and synovial fluid cultures (SFCs). The JI Panel detected more positive samples and microorganisms than SFC, with a notable difference on Staphylococcus aureus, Streptococcus species, Enterococcus faecalis, Kingella kingae, Neisseria gonorrhoeae, and anaerobic bacteria. The study found that the BIOFIRE JI Panel has a high utility in the real-world clinical setting for suspected SA and PJI, providing diagnostic results in approximately 1 h. The user experience was positive, implying a potential benefit of rapidity of results' turnover in optimising patient management strategies. Conclusion: The study suggests that the BIOFIRE JI Panel could potentially optimise patient management and antimicrobial therapy, thus highlighting its importance in the clinical setting.

Intracellular activity and in vivo efficacy in a mouse model of septic arthritis of the novel pseudopeptide Pep16 against Staphylococcus aureus clinical isolates

Objectives

Assessing the therapeutic potential of a novel antimicrobial pseudopeptide, Pep16, both in vitro and in vivo for the treatment of septic arthritis caused by Staphylococcus aureus.

Methods

Seven clinical isolates of S. aureus (two MRSA and five MSSA) were studied. MICs of Pep16 and comparators (vancomycin, teicoplanin, daptomycin and levofloxacin) were determined through the broth microdilution method. The intracellular activity of Pep16 and levofloxacin was assessed in two models of infection using non-professional (osteoblasts MG-63) or professional (macrophages THP-1) phagocytic cells. A mouse model of septic arthritis was used to evaluate the in vivo efficacy of Pep16 and vancomycin. A preliminary pharmacokinetic (PK) analysis was performed by measuring plasma concentrations using LC-MS/MS following a single subcutaneous injection of Pep16 (10 mg/kg).

Results

MICs of Pep16 were consistently at 8 mg/L for all clinical isolates of S. aureus (2- to 32-fold higher to those of comparators) while MBC/MIC ratios confirmed its bactericidal activity. Both Pep16 and levofloxacin (when used at 2 × MIC) significantly reduced the bacterial load of all tested isolates (two MSSA and two MRSA) within both osteoblasts and macrophages. In MSSA-infected mice, Pep16 demonstrated a significant (∼10-fold) reduction on bacterial loads in knee joints. PK analysis following a single subcutaneous administration of Pep16 revealed a gradual increase in plasma concentrations, reaching a peak of 5.6 mg/L at 12 h.

Conclusions

Pep16 is a promising option for the treatment of septic arthritis due to S. aureus, particularly owing to its robust intracellular activity.

Tuberculous Septic Arthritis of the Hip Following the Incision and Drainage of a Groin Abscess: A Case Report

Tuberculosis of the hip is a relatively rare type of septic arthritis that is seldom seen in the developed world today. While pyogenic septic arthritis may present with clear features that help in early diagnosis and treatment, many of these features are absent or overlap significantly with tuberculous arthritis, making the diagnosis a clinical challenge. Here, we present a case of tuberculous septic arthritis seen in our clinic following the surgical incision and drainage of a groin abscess with minimal hip symptoms. We discuss the therapeutic approach for the patient and briefly review other reported cases of tuberculous septic arthritis in the literature.

Endogenous blocking of TLR2 along with TNF-α and IL-1β ameliorates the severity of the S. aureus arthritis via modulating STAT3/SOCS3 expressions in tissue resident macrophages

In vivo studies identifying a role of TLR2 in septic arthritis models are lacking. TNF-α played as the most important proinflammatory cytokine, and connected directly to the pathogenesis of bacterial arthritis. IL-1β is another central mediator cytokine in arthritis. It is therefore reasonable to question the role of neutralization of endogenous TNF-α and IL-1β along with TLR2 and associated downstream signaling as crucial mediators in the S. aureus -induced inflammatory arthritis. In reaction to an injury or a pathogen encounter, innate immune cells serve as the initial line of defense. TLR2 mediated entry of S. aureus into macrophage cells initiates an array of inflammatory cascades. After macrophage cell gets activated at the site inflammation, they generate elevated number of cytokines which includes TNF-α, IL-1β. This cytokines signals through STAT1/STAT3 mediated pathways. Thus, aim of this study was to discover how This bone damage could be altered by altering the STAT/STAT3/SOCS3 ratio by blocking TLR2, a particular S. aureus binding site, in conjunction with the use of IL-1 and TNF- antibodies for neutralizing endogenous IL-1β and TNF-α. Additionally, the role of local macrophages in therapy of arthritis was investigated in synovial and Splenic tissue. To comprehend the inflammatory milieu within the system, ROS and other antioxidant enzymes, along with the expression of mTOR in macrophage cells, were also taken into consideration. The detrimental impact of bacterial burden on synovial joints was reduced by simultaneously inhibiting TLR2, TNF-α, and IL-1β. Lowered IFN-γ decreases its sensitivity to STAT1 and lowered IL-6 reduces STAT3 expressions. Whereas, elevated IL-10 enhances SOSC3 expression, which thereby able to limits STAT1/STAT3 inter-conversion. As a result, NF-κB activity was downregulated.

Methicillin Resistance Increased the Risk of Treatment Failure in Native Joint Septic Arthritis Caused by Staphylococcus aureus

This study aimed to compare clinical characteristics and outcomes in patients with native joint septic arthritis (NJSA) due to methicillin-resistant Staphylococcus aureus (MRSA) in comparison to methicillin-sensitive S. aureus (MSSA) and identify treatment failure risk factors. We conducted a multi-center retrospective study on adult NJSA patients at three teaching hospitals in South Korea from 2005 to 2017. Among 101 patients diagnosed with S. aureus NJSA, 39 (38.6%) had MRSA strains. Compared to MSSA, patients with MRSA had a higher prevalence of nosocomial infections (17.9% vs. 1.6%; p = 0.005) and received inappropriate antibiotics within 48 h more frequently (74.4% vs. 0%; p < 0.001). In total, twenty patients (19.8%) experienced treatment failure, which encompassed five patients (5.0%) who passed away, nine (8.9%) requiring repeated surgical drainage after 30 days of antibiotic therapy, and seven (6.9%) with relapse. The MRSA group showed a higher rate of overall treatment failure (33.3% vs. 11.3%; p = 0.007) with a notably increased frequency of requiring repeated surgical interventions after 30 days of antibiotic therapy (17.9% vs. 3.2%, p = 0.026), in contrast to the MSSA group. Independent risk factors for treatment failure included Charlson comorbidity score, elevated CRP levels, and methicillin resistance. Methicillin resistance is an independent risk factor for treatment failure, emphasizing the need for vigilant monitoring and targeted interventions in MRSA-related NJSA cases.

Case Report and Literature Review of Parvimonas micra: Difficult-to-Treat Arthritis in Hiding

Septic arthritis is a life-threatening rheumatological syndrome that is highly related to a patient's immune status and comorbidities, and although the most common clinical presentation is rapid-onset monoarthritis, it can also appear as subacute or chronic joint swelling. In these cases, differential diagnosis is more challenging, but early diagnosis and treatment is no less urgent to ensure a good global prognosis and the best outcome of the affected joint. Anaerobic microorganisms, such as Parvimonas micra, are an uncommon cause of septic arthritis (less than 5% of cases) but may be the cause of subacute arthritis. Knowledge about Parvimonas micra is important, as it is difficult to culture in the laboratory and generates a synovial fluid with atypical characteristics for septic arthritis so that, if not suspected, its diagnosis can be easily overlooked and underdiagnosed. We present the case of a 76-year-old woman with subacute arthritis of the left knee, describe the difficult diagnosis and treatment of its unexpected cause (Parvimonas micra), and review previously described cases, identifying the possible common comorbidities that may help clinicians easily find and treat this cause of subacute septic arthritis.

Administering Antibiotics for Less Than Four Weeks Increases the Risk of Relapse in Culture-Positive Septic Arthritis of Native Joints

(1) Objectives: This study investigated the optimal duration of antibiotic therapy and determined the risk factors associated with relapse in patients with culture-proven septic arthritis of native joints. (2) Methods: A retrospective review was conducted on patients aged ≥18 years diagnosed with native joint septic arthritis, with bacteria isolated from joints and/or blood. The exclusion criteria were prosthetic joint infections and cases with no identified microorganisms. The outcomes were assessed in the remission and relapse groups. (3) Results: Among 479 patients with native joint septic arthritis, 137 met the inclusion criteria, with a median follow-up duration of 2.7 years. The relapse rate was 9.5%, which mainly occurred within 30 days after antibiotic treatment completion. Compared with the remission group, the relapse group showed a significantly higher proportion of cases that received antibiotic therapy for ≤ 4 weeks (4.8% vs. 46.2%, p < 0.001), synovial fluid white blood cell (WBC) counts ≥150 × 103/mm3 (25.3% vs. 60.0%, p = 0.030), acute kidney injury (19.2% vs. 50%, p = 0.024), and extended-spectrum beta-lactamases-producing Enterobacteriaceae (0.8 vs. 15.4%, p = 0.024). Independent risk factors for relapse were determined as antibiotic therapy duration of ≤ 4 weeks (odds ratio (OR), 25.47; 95% confidence interval (CI), 1.57-412.33; p = 0.023) and synovial fluid WBC counts ≥150 × 103/mm3 (OR, 17.46; 95% CI, 1.74-175.62; p = 0.015). (4) Conclusions: Patients with native joint septic arthritis require vigilant monitoring for relapse, particularly when treated with antibiotic regimens administered for less than four weeks or when synovial aspirates exhibit elevated WBC counts at diagnosis.

Septic Arthritis of the Knee in Children

Septic arthritis of the knee is the most common form of septic arthritis in children and can lead to irreversible damage to the joint. Staphylococcus aureus is the primary pathogen associated with septic arthritis, although other causative pathogens may be isolate in children with specific risk factors. The diagnosis of knee septic arthritis is based on comprehensive evaluation, including the patient's medical history, physical examination, blood tests, and arthrocentesis. Empirical treatment typically involves anti-staphylococcal penicillin or a first-generation cephalosporin, although modifications may be made based on local resistance patterns and clinical culture data. Surgical debridement, either through open surgery or arthroscopy, involving extensive debridement of the joint, is effective in eliminating the infection. In most cases, additional surgical intervention is not necessary.