Leukocyte count in the synovial fluid of children with culture-proven brucellar arthritis

Joint Fluid Cell Count in Acute Bacterial Arthritis Patients Proven Positive Culture in Children

BACKGROUND

Acute bacterial arthritis (ABA) is a serious, pediatric infection that can result in motor comorbidities. Normally, a joint fluid white blood cell (WBC) count of 50,000 or more cells/mm3 is used to make a presumptive diagnosis of ABA. This study evaluated the utility of the joint fluid WBC count for diagnosing pediatric ABA confirmed by a positive culture result.

METHODS

Patients with ABA between March 2010 and March 2023 at Tokyo Metropolitan Children's Medical Center were included. ABA was confirmed by positive joint fluid culture results for a pathogenic organism. Patients with negative results and those without a joint fluid WBC count were excluded. Electronic medical records were retrospectively reviewed for demographic data, timing of arthrocentesis, culture results and the joint fluid WBC count.

RESULTS

Ninety-five patients with ABA were identified; of these, 22 were included. The median age was 5 years [interquartile range (IQR): 2-10 years]. Males comprised 55% of the population. The median joint fluid WBC count was 19,575 (IQR: 6806-47,388) cells/mm3, and 23% of the patients had 50,000 cells/mm3 or more. The median time from symptom onset to arthrocentesis was 3 days (IQR: 2-5 days). The isolated organisms were methicillin-susceptible Staphylococcus aureus (50%), methicillin-resistant S. aureus (9%), Streptococcus pyogenes (27%), Streptococcus pneumoniae (5%), Klebsiella pneumoniae (5%) and Salmonella spp. (5%).

CONCLUSIONS

Most of the patients with ABA confirmed by positive results of a joint fluid culture had a joint fluid WBC count of less than 50,000 cells/mm3.

Acute Arthritis in Children: How to Discern between Septic and Non-Septic Arthritis?

The term septic arthritis refers to an infection of the synovial space. This is an infrequent condition in healthy children, but it should be considered a medical emergency potentially leading to irreversible articular damage. Therefore, prompt diagnosis and antimicrobial treatment play a crucial role in improving the prognosis. Although septic arthritis is the most common cause of acute arthritis, many other diseases may mimic a similar clinical picture, constituting a diagnostic challenge for the clinician who first approaches the patient. Herein we analyze the main features of septic arthritis, offering an overview of the main conditions involved in the differential diagnosis and suggesting a diagnostic workup plan.

Factors Associated With Single and Recurrent Bacteremia in Childhood Brucellosis

BACKGROUND

Data regarding risk factors of bacteremic brucellosis, and specifically recurrent bacteremia, are scarce. We assessed patients with childhood brucellosis, differentiating between those having culture-negative, single-bacteremic, and recurrent-bacteremic episodes.

METHODS

The medical files of pediatric brucellosis patients, from 2005 through 2014, were reviewed retrospectively. Univariate and multivariate analyses were performed to compare demographic and clinical characteristics of culture-negative, single-bacteremic, and recurrent-bacteremic (≥30 days between positive cultures) episodes.

RESULTS

Of all 436 brucellosis cases, 22% were culture-negative, 72% were single-bacteremic, and 6% were recurrent-bacteremic. In a univariate analysis, single-bacteremic episodes were associated with fever (90% vs 65% and 40% in culture-negative and recurrent bacteremia, respectively) and elevated glutamic oxaloacetic transaminase (GOT) levels. Recurrent-bacteremic episodes were associated with anemia (26% vs 14% and 9% in single bacteremia and culture negative, respectively), elevated GOT, low immunoglobulin M (IgM) titers (56% vs 89% and 99%, respectively), and lower levels of adequate treatment (74% vs 94% and 86%, respectively). In multivariate analyses, single bacteremia was associated with fever (odds ratio [OR], 3.595, compared with culture negative), while recurrent bacteremia was inversely associated with IgM titers ≥1:160 (OR, 0.022 and 0.226 compared with culture negative and single bacteremia, respectively) and fever (OR, 0.108 compared with single bacteremia).

CONCLUSIONS

Brucellosis episodes are commonly complicated with bacteremia. Single-bacteremic episodes were associated with high-grade fever and elevated liver enzymes, possibly indicating high bacterial virulence. Recurrent-bacteremic episodes were associated with poor treatment at initial diagnosis, along with low rates of fever, low IgM titers, and high anemia rates, possibly indicating impaired host response. Physicians should consider treatment modifications for suspected recurrent-bacteremic brucellosis, including monitoring treatment adherence, and possibly administering prolonged treatment.

Septic arthritis in children: Updated epidemiologic, microbiologic, clinical and therapeutic correlations

BACKGROUND

Septic arthritis (SA) is an infection characterized by significant epidemiologic and microbiologic differences between developed and developing regions and between age groups.

OBJECTIVES

To determine the epidemiologic, clinical, microbiologic and therapeutic aspects of pediatric SA in Southern Israel.

METHODS

A retrospective case-series study based on the records of children <16 years of age admitted with SA at Soroka Medical Center, Beer-Sheva, during 2006-2013.

RESULTS

189 patients were enrolled. There were 119 (63%) Bedouin and 70 (37%) Jewish children. The knee (39.7%), hip (28%) and ankle (13.8%) were the most commonly involved joints. Blood and/or synovial fluid cultures were positive in 48 (25.4%) patients. Overall SA incidence among children <16 years and <5 years was 11.7 and 25.4/100,000, respectively, without changes throughout the study period. SA incidence among Bedouin children was higher than among Jewish children (15.4 vs. 8.3/100,000 cases). Staphylococcus aureus was the most commonly isolated pathogen (18, 19.5% of all patients), followed by Kingella kingae (10, 5.3%)-(37.5% and 20.8% among culture-positive patients, respectively). The number of children with culture-positive SA that required surgery was higher than those with culture-positive SA treated conservatively (P < 0.001). Hospitalization was longer in children treated surgically than in those treated conservatively (P < 0.001).

CONCLUSION

This study is the largest single-center series on pediatric SA published in the last five years and provided an updated picture on incidence and the microbiologic, clinical and therapeutic aspects of pediatric SA in Southern Israel. The study supports a regional presentation pattern of SA and may guide its therapeutic management.

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.

IFN-γ-dependent nitric oxide suppresses Brucella-induced arthritis by inhibition of inflammasome activation

Brucellosis, caused by the intracellular bacterial pathogen Brucella, is a globally important zoonotic disease for which arthritis is the most common focal complication in humans. Wild-type mice infected systemically with Brucella typically do not exhibit arthritis, but mice lacking IFN-γ develop arthritis regardless of the route of Brucella infection. Here, we investigated mechanisms by which IFN-γ suppresses Brucella-induced arthritis. Several cell types, including innate lymphoid cells, contributed to IFN-γ production and suppression of joint swelling. IFN-γ deficiency resulted in elevated joint IL-1β levels, and severe joint inflammation that was entirely inflammasome dependent, and in particular, reliant on the NLRP3 inflammasome. IFN-γ was vital for induction of the nitric oxide producing enzyme, iNOS, in infected joints, and nitric oxide directly inhibited IL-1β production and inflammasome activation in Brucella-infected macrophages in vitro. During in vivo infection, iNOS deficiency resulted in an increase in IL-1β and inflammation in Brucella-infected joints. Collectively, this data indicate that IFN-γ prevents arthritis both by limiting Brucella infection, and by inhibiting excessive inflammasome activation through the induction of nitric oxide.

Microbiological Diagnosis of Skeletal System Infections in Children

BACKGROUND

If not timely diagnosed and adequately treated, skeletal system infections in children may result in severe and permanent disability. Prompt identification of the etiology of the disease and determination of its antibiotic susceptibility are crucial for the successful management of septic arthritis, osteomyelitis, and spondylodiscitis. However, the bacteriological diagnosis of these infections has been traditionally limited by the low yield of conventional cultures and, on average, one-third of cases of pediatric joint and bone infections remained unconfirmed.

OBJECTIVE

To review the medical literature to summarize the current approach diagnosing the pediatric skeletal system infections.

METHODS

The relevant publications for the last three decades were reviewed.

RESULTS

In recent years, the detection of skeletal system pathogens has been revolutionized by the use of improved laboratory methods, including seeding of synovial fluid and bone exudates into blood culture vials, and the development and implementation of sensitive nucleic acid amplification assays. These advances have resulted in the recognition of Kingella kingae as the predominant etiology of hematogenous infections of bones, joints, intervertebral discs and tendon sheaths in children aged 6-48 months, and reduced the fraction of culture-negative osteoarthritis.

CONCLUSION

As the exudate and tissue samples obtained from young children with skeletal system infections are frequently insufficient for a comprehensive laboratory workup, physicians should take in consideration the patient's age, predisposing medical conditions and possible exposure to zoonotic organisms, and use a judicious combination of Gram's stain, culture on blood culture vials, and molecular tests to maximize the microbiological diagnosis of these diseases.

Caspase-1 and Caspase-11 Mediate Pyroptosis, Inflammation, and Control of Brucella Joint Infection

Brucellosis, caused by the intracellular bacterial pathogen Brucella, is a zoonotic disease for which arthritis is the most common focal complication in humans. Here we investigated the role of inflammasomes and their effectors, including interleukin-1 (IL-1), IL-18, and pyroptosis, on inflammation and control of infection during Brucella-induced arthritis. Early in infection, both caspase-1 and caspase-11 were found to initiate joint inflammation and proinflammatory cytokine production. However, by 1 week postinfection, caspase-1 and caspase-11 also contributed to control of Brucella joint infection. Inflammasome-dependent restriction of Brucella joint burdens did not require AIM2 (absent in melanoma 2) or NLRP3 (NLR family, pyrin domain containing 3). IL-1R had a modest effect on Brucella-induced joint swelling, but mice lacking IL-1R were not impaired in their ability to control infection of the joint by Brucella In contrast, IL-18 contributed to the initiation of joint swelling and control of joint Brucella infection. Caspase1/11-dependent cell death was observed in vivo, and in vitro studies demonstrated that both caspase-1 and caspase-11 induce pyroptosis, which limited Brucella infection in macrophages. Brucella lipopolysaccharide alone was also able to induce caspase-11-dependent pyroptosis. Collectively, these data demonstrate that inflammasomes induce inflammation in an IL-18-dependent manner and that inflammasome-dependent IL-18 and pyroptosis restrict Brucella infection.

Brucella and Osteoarticular Cell Activation: Partners in Crime

Osteoarticular brucellosis is the most common presentation of human active disease although its prevalence varies widely. The three most common forms of osteoarticular involvement are sacroiliitis, spondylitis, and peripheral arthritis. The molecular mechanisms implicated in bone damage have been recently elucidated. B. abortus induces bone damage through diverse mechanisms in which TNF-α and the receptor activator of nuclear factor kappa-B ligand (RANKL)-the natural modulator of bone homeostasis are involved. These processes are driven by inflammatory cells, like monocytes/macrophages, neutrophils, Th17 CD4⁺ T, and B cells. In addition, Brucella abortus has a direct effect on osteoarticular cells and tilts homeostatic bone remodeling. These bacteria inhibit bone matrix deposition by osteoblasts (the only bone cells involved in bone deposition), and modify the phenotype of these cells to produce matrix metalloproteinases (MMPs) and cytokine secretion, contributing to bone matrix degradation. B. abortus also affects osteoclasts (cells naturally involved in bone resorption) by inducing an increase in osteoclastogenesis and osteoclast activation; thus, increasing mineral and organic bone matrix resorption, contributing to bone damage. Given that the pathology induced by Brucella species involved joint tissue, experiments conducted on synoviocytes revealed that besides inducing the activation of these cells to secrete chemokines, proinflammatory cytokines and MMPS, the infection also inhibits synoviocyte apoptosis. Brucella is an intracellular bacterium that replicates preferentially in the endoplasmic reticulum of macrophages. The analysis of B. abortus-infected synoviocytes indicated that bacteria also replicate in their reticulum suggesting that they could use this cell type for intracellular replication during the osteoarticular localization of the disease. Finally, the molecular mechanisms of osteoarticular brucellosis discovered recently shed light on how the interaction between B. abortus and immune and osteoarticular cells may play an important role in producing damage in joint and bone.

CXCR2 Mediates Brucella-Induced Arthritis in Interferon γ-Deficient Mice

BACKGROUND

Brucella species are facultative intracellular gram-negative bacteria that cause brucellosis, a common global zoonosis. Infection of the joints is the most common focal complication of brucellosis in humans. The purpose of this study was to identify mediators of focal inflammation during brucellosis.

METHODS

Wild-type (WT) mice are naturally resistant to Brucella infection; therefore, we infected anti-interferon γ (IFN-γ)-treated, or IFN-γ(-/-) mice with Brucella to induce osteoarticular and musculoskeletal inflammation, as we previously described. Mice were infected intraperitoneally with Brucella melitensis, and the clinical course of disease, histopathologic changes, and cytokine levels were compared among groups.

RESULTS

Rag1(-/-) mice (B- and T-cell deficient) and µMT(-/-) mice (B-cell deficient) developed paw inflammation at a similar rate and severity as WT mice following infection with B. melitensis and treatment with anti-IFN-γ. Joints from B. melitensis-infected IFN-γ(-/-) mice had markedly increased levels of CCR2 and CXCR2 ligands. While anti-IFN-γ-treated CCR2(-/-) and WT mice behaved similarly, anti-IFN-γ-treated CXCR2(-/-) or IFN-γ(-/-)/CXCR2(-/-) mice had strikingly reduced focal swelling relative to anti-IFN-γ-treated WT or IFN-γ(-/-) mice, respectively. Additionally, neutrophil recruitment was dependent on CXCR2.

CONCLUSIONS

Adaptive immune cells and CCR2 are dispensable, while CXCR2 is necessary for Brucella-induced focal neutrophil recruitment and inflammation.

Acute brucellosis: presentation, diagnosis, and treatment of 144 cases

OBJECTIVES

Brucellosis, whether in an endemic region or not, remains a diagnostic puzzle due to occasional misleading unusual presentations and non-specific symptoms. Presented herein is our 14-year experience with acute brucellosis at Sparta General Hospital, Lakonia, Greece.

METHODS

A case series of 144 patients admitted to the internal medicine, pediatrics, and urology departments, through evaluation of history, occupational data, serological tests, cultures of blood and other body fluids, and imaging studies. Patients were treated with a 21-day course of intramuscular streptomycin and a prolonged two-month course of doxycycline with a six-month follow-up.

RESULTS

Infected patients had a relevant occupational history in fewer than 20% of cases. Clinical manifestations included non-specific symptoms (fever, malaise, sweats, arthralgias, lower back pain, headache), findings such as splenomegaly (51%), osteoarticular involvement (42%), cervical lymphadenitis (31%), hepatomegaly (25%), genitourinary involvement (13% of men), cholecystitis (2%), breast abscess (0.7%), and acute abdomen (0.7%). Ninety-five percent of the patients had a serological titer > or =1/160 with culture-proven brucellosis. Overall, 82% of blood cultures and 100% of other body fluid cultures (synovial, bile) were positive. Ninety-seven percent of the patients were cured. Relapse in the follow-up period was observed in four patients who had not complied with treatment.

CONCLUSIONS

Brucellosis is an infection with multiple presentations, and whether in an endemic region or not, a thorough history of exposure and clinical suspicion are required since thresholds in serological evaluation may lead to misdiagnosis and withholding of adequate treatment.

A case of brucellar septic arthritis of the knee with a prolonged clinical course

Brucellosis is a systemic infectious disease with a broad spectrum of clinical manifestations. Arthritis is frequently observed in its course and may be one of the main presenting clinical features of the disease. We report a case of brucellar monoarthritis of the knee with a prolonged clinical course despite efficient antibiotic treatment.