Differentiating Kingella kingae septic arthritis of the hip from transient synovitis in young children

Clinical and Biologic Characteristics of Kingella kingae -Induced Septic Arthritis of the Knee in Young Children

BACKGROUND AND OBJECTIVES

Septic arthritis of the knee is presumed to be the most frequent form of Kingella kingae -induced osteoarticular infection. This study aimed to report on the clinical course, biological parameters, and results of microbiological investigations among children with K. kingae -induced septic arthritis of the knee. It also assessed the modified Kocher-Caird criteria's ability to predict K. kingae -induced septic arthritis of the knee.

METHODS

The medical charts of 51 children below 4 years old with confirmed or highly probable K. kingae -induced arthritis of the knee were reviewed. Data were gathered on the five variables in the commonly-used Kocher-Caird prediction algorithm (body temperature, refusal to bear weight, leukocytosis, erythrocyte sedimentation rate, and C-reactive protein level).

RESULTS

Patients with K. kingae -induced arthritis of the knee usually presented with a mildly abnormal clinical picture and normal or near-normal serum levels of acute-phase reactants. Data on all five variables were available for all the children: 7 children had zero predictors; 8, 20, 12, and 4 children had 1, 2, 3, and 4 predictors, respectively; no children had 5 predictors. This gave an average of 1.96 predictive factors and a subsequent probability of ≤ 62.4% of infectious arthritis in this pediatric cohort.

CONCLUSIONS

Because the clinical features of K. kingae -induced arthritis of the knee overlap with many other conditions affecting this joint, the Kocher-Caird prediction algorithm is not sensitive enough to effectively detect K. kingae -induced septic arthritis of the knee. Excluding K. kingae -induced arthritis of the knee requires performing nucleic acid amplification assays on oropharyngeal swabs and joint fluid from those young children presenting with effusion of the knee, even in the absence of fever, leukocytosis, or a high Kocher-Caird score.

The Past, Present, and Future of Kingella kingae Detection in Pediatric Osteoarthritis

As a result of the increasing use of improved detection methods, Kingella kingae, a Gram-negative component of the pediatric oropharyngeal microbiota, is increasingly appreciated as the prime etiology of septic arthritis, osteomyelitis, and spondylodiscitis in children aged 6 to 48 months. The medical literature was reviewed to summarize the laboratory methods required for detecting the organism. Kingella kingae is notoriously fastidious, and seeding skeletal system samples onto solid culture media usually fails to isolate it. Inoculation of synovial fluid aspirates and bone exudates into blood culture vials enhances Kingella kingae recovery by diluting detrimental factors in the specimen. The detection of the species has been further improved by nucleic acid amplification tests, especially by using species-specific primers targeting Kingella kingae's rtxA, groEL, and mdh genes in a real-time PCR platform. Although novel metagenomic next-generation technology performed in the patient's plasma sample (liquid biopsy) has not yet reached its full potential, improvements in the sensitivity and specificity of the method will probably make this approach the primary means of diagnosing Kingella kingae infections in the future.

Predictive Algorithms in the Diagnosis and Management of Pediatric Hip and Periarticular Infection

➤ Although the criteria of Kocher et al. were an important advancement in our ability to diagnose septic arthritis of the hip early, the changing microbial landscape and availability of advanced imaging have rendered it insufficient for contemporary clinical use.➤ Routine use of magnetic resonance imaging and recognition of disseminated disease have prompted the development of algorithms to predict concurrent osteoarticular infection in cases of septic arthritis and osteomyelitis that were previously assumed to be "isolated."➤ Recent research has attempted to stratify childhood bone and joint infection (BJI) by severity to guide treatment planning. This is valuable, as patients with multifocal disease, more virulent pathogens, and immunocompromise can have longer hospital stays and require multiple surgeries.➤ The increasing prevalence of clinical prediction algorithms in childhood BJI is not completely matched by quality in methodology. Clinicians need to be wary of adopting predictive algorithms prior to robust external validation.

Kingella kingae Osteoarticular Infections Approached through the Prism of the Pediatric Orthopedist

Nowadays, Kingella kingae (K. kingae) is considered as the main bacterial cause of osteoarticular infections (OAI) in children aged less than 48 months. Next to classical acute hematogenous osteomyelitis and septic arthritis, invasive K. kingae infections can also give rise to atypical osteoarticular infections, such as cellulitis, pyomyositis, bursitis, or tendon sheath infections. Clinically, K. kingae OAI are usually characterized by a mild clinical presentation and by a modest biologic inflammatory response to infection. Most of the time, children with skeletal system infections due to K. kingae would not require invasive surgical procedures, except maybe for excluding pyogenic germs' implication. In addition, K. kingae's OAI respond well even to short antibiotics treatments, and, therefore, the management of these infections requires only short hospitalization, and most of the patients can then be treated safely as outpatients.

Changing aetiology of paediatric septic arthritis

The management of septic arthritis in children requires the prompt administration of antibiotic therapy and the identification of the causative pathogen. In the past, Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae and Haemophilus influenzae type b were considered the main causative agents of the disease, but a substantial fraction of presumptive joint infections remained unconfirmed by conventional bacteriologic cultures. In the last two decades, our knowledge of the aetiology of paediatric infectious arthritis has substantially changed as the result of the implementation of vaccination programmes against H. influenzae type b and pneumococci, and by the use of improved detection methods. In 1988, the inoculation of synovial fluid aspirates into blood culture vials revealed that Kingella kingae, a commensal member of the oropharyngeal microbiota, was the prime aetiology of skeletal system infections in children aged 6-48 months. The clinical presentation of K. kingae arthritis is subtle, and the disease is frequently missed by classic clinical and laboratory diagnostic criteria. Many children are afebrile, the acute phase reactants levels and the white blood cell counts in the blood and synovial fluid specimens are frequently normal, requiring a high clinical acumen. Increasing use of sensitive molecular methods in recent years, and particularly nucleic acid amplification tests that target K. kingae-specific genes, has further improved the detection of this elusive pathogen, demonstrated that it is responsible for 30-93% of all cases of septic arthritis below 4 years of age and reduced the fraction of culture-negative infections.

Review highlights the latest research in Kingella kingae and stresses that molecular tests are required for diagnosis

AIM

The aim of this study was to provide an update on paediatric Kingella kingae infections.

METHODS

We used the PubMed database to identify studies published in English, French and Spanish up to 15 November 2020.

RESULTS

Kingella kingae colonised the oropharynx after the age of 6 months, and the mucosal surface was the portal of entry of the organism to the bloodstream and the source of child-to-child spread. Attending day care centres was associated with increased carriage rate and transmission and disease outbreaks were detected in day care facilities. Skeletal system infections were usually characterised by mild symptoms and moderately elevated inflammation markers, requiring a high clinical suspicion index. The organism was difficult to recover in cultures and molecular tests significantly improve its detection. Kingella kingae was generally susceptible to beta-lactam antibiotics, and skeletal diseases and bacteraemia responded to antimicrobial, leaving no long-term sequelae. However, patients with endocarditis frequently experienced life-threatening complications and the case fatality rate exceeded 10%.

CONCLUSION

Kingella kingae was the prime aetiology of skeletal system infections in children aged 6-48 months. Paediatricians should be aware of the peculiar features of this infection and the need to use molecular tests for diagnosis.

Oropharyngeal Carriage of Kingella kingae and Transient Synovitis of the Hip in Young Children: A Case-control Study

BACKGROUND

Transient synovitis of the hip affects mostly preschool children, and its etiology is unknown. Kingella kingae has been identified recently as a common etiologic agent of osteoarticular infections (OAI) in young children and could potentially be associated to transient synovitis of the hip. The main objective of this study was to evaluate the association between transient synovitis of the hip and oropharyngeal carriage of K. kingae among preschool children.

METHODS

This was a prospective case-control study conducted at a tertiary care pediatric emergency department. Cases were children between 6 and 71 months of ages with a diagnosis of transient synovitis of the hip. For each transient synovitis case, an age-matched control was recruited among children presenting for a trauma. A second control group included children with any OAI. The independent variable was the presence of oropharyngeal K. kingae identified by a specific polymerase chain reaction assay. The primary analysis was the association between oropharyngeal K. kingae carriage and final diagnosis.

RESULTS

A total of 73 children were included in the study. Among them, 25 had a transient synovitis, 16 an OAI, and 22 controls. Baseline demographics were similar between the groups. There was no difference in oropharyngeal carriage of K. kingae for children with transient synovitis (5/25; 0.20) in comparison to controls (3/22; 0.14), while it was higher for children with OAI (10/16; 0.63).

CONCLUSIONS

There is no association between oropharyngeal K. kingae and transient synovitis of the hip among preschool children.

Primary Septic Arthritis Among Children 6 to 48 Months of Age: Implications for PCR Acquisition and Empiric Antimicrobial Selection

INTRODUCTION

Primary septic arthritis requires unique evaluation and treatment considerations for children in the 6- to 48-month age range because of the spectrum of identified pathogens and high rate of negative cultures. The purpose of this study is to evaluate primary septic arthritis in this age group in order to differentiate children with infection caused by Kingella kingae from those with other confirmed pathogens and those with no identified pathogen.

METHODS

Preschool children who underwent multidisciplinary evaluation and treatment for septic arthritis between 2009 and 2019 were retrospectively studied. Three cohorts were established for comparison of clinical and laboratory features of primary septic arthritis: (1) confirmed K. kingae, (2) confirmed other pathogen, and (3) presumed (without identified pathogen).

RESULTS

Among 139 children with septic arthritis, 40 (29%) were confirmed K. kingae, 29 (21%) other pathogen, and 70 (50%) presumed. Children with Kingella and those with presumed septic arthritis had significantly lower initial C-reactive protein (4.8 and 4.5 vs. 9.3 mg/dL) and fewer febrile hospital days (0.2 and 0.4 vs. 1.3 d) than children with other confirmed pathogens. Children with other pathogens had higher rates of bacteremia (38% vs. 0%) and positive joint fluid cultures (86% vs. 15%) than that of children with Kingella. The rate of polymerase chain reaction (PCR) acquisition was 38 of 40 (95.0%) Kingella cases, 18 of 29 (62.1%) other pathogen cases, and 33 of 70 (47.1%) presumed cases.

CONCLUSIONS

K. kingae was the most commonly identified pathogen among 6-month to 4-year-old children. The Kingella and other identified pathogens in this study serve to guide empiric antimicrobial recommendations for this age range. Because of similarities between children with septic arthritis because of K. kingae and those with no identified pathogen, it is likely that an unrecognized burden of Kingella resides in culture negative cases, particularly if no PCR is sent. Systematic evaluation, including PCR acquisition, and a high index of suspicion for K. kingae are recommended to thoroughly evaluate septic arthritis in preschool children.

LEVEL OF EVIDENCE

Level III-Retrospective cohort comparison.

Epidemiology of Irritable Hip in Western Scotland: A Follow-Up Study

Background

A ‘limping child’ commonly presents to the emergency department (ED). In the absence of trauma, many are diagnosed with irritable hip (IH). The aetiology of IH is not well understood and there may be geographical and seasonal variations. We previously established one year (2016) epidemiological data of IH presenting to the Royal Hospital for Children (RHCG) ED in Glasgow, Scotland. The sentinel findings in that year were (i) an age distribution shift to younger (peak at two years of age), (ii) no marked association with social class, and (iii) a spring preponderance. We sought to strengthen or refute these findings by repeating our study to obtain comparative data for 2017.

Methods

We performed a retrospective analysis of all children discharged from the RHCG ED from January to December 2017. Relevant discharge codes were determined, and patient records screened. Patients without a discharge code had their presenting complaint and medical record screened. These data were compared to that of the previously published study from the same ED (2016).

Results

Several findings were consistent with the conclusions of the 2016 study. The incidence was similar with 362 and 354 cases diagnosed in 2017 and 2016 respectively. The boy-girl ratio was consistent across both data-sets, 2:1 and 1.9:1 respectively. The mean age of presentation was similar (3.3 vs 3.5 years) across both years, with the same medians (three years) and peaks (two years). There was no overt difference in incidence or correlation to social deprivation. However, in 2016, a spring preponderance was seen whereas there was an autumn preponderance in 2017. Pooling data from the two cohorts, 93% (n=668) of patients were managed exclusively by ED physicians, with 70% (n=504) not requiring any further follow-up. The majority of patients who required follow-up were seen in ED clinics (169/212, 79.7%). No patient initially diagnosed as IH was found to have septic arthritis (SA).

Conclusion

In this follow-up study, we again found (i) a younger age profile than other studies, and (ii) no overt association with social deprivation. The major difference between the previous (2016) and current (2017) study was the apparent seasonal peaks: spring (2016), and autumn (2017). This difference does not negate the 'antecedent infection' hypothesis, but any aetiological proposal should be capable of accounting for this discrepancy. Additionally, our studies highlight that the majority of these patients can be managed in the ED alone.

The Utility of Leukocyte Esterase Strip Test in the Diagnosis of Pediatric Septic Arthritis

BACKGROUND

Most tests used to diagnose pediatric septic arthritis are either not accurate or do not produce rapid results. A leukocyte esterase (LE) strip test has previously been validated for the diagnosis of adult native and periprosthetic joint infections. The purpose of this prospective study was to: (1) evaluate the performance characteristics of the LE strip test in the diagnosis of pediatric septic arthritis and (2) determine the false positive rate of LE strip test on the aseptic synovial fluid (SF).

METHODS

Between May 2016 and November 2018, SF was obtained from children who were hospitalized at our tertiary referral center on the basis of suspicion of septic arthritis. All patients underwent arthrocentesis, and the aspirate was tested with LE strip test, leukocyte count, and culture. Twenty-five patients satisfied the inclusion criteria. For the second part of the study, SF from 25 children undergoing surgery for developmental dysplasia of the hip was collected and tested with LE strip test, leukocyte count, and culture.

RESULTS

In the first part of this study, 19 joints were classified as septic and 6 as aseptic. Considering a positive LE strip test ("++" and "+++" readings) indicative of septic arthritis yielded a sensitivity of 100%, specificity of 83%, positive predictive value of 95%, and negative predictive value of 100%. In the second part, all 25 patients with an aseptic SF had a negative test result ("-" and "+" readings).

CONCLUSIONS

The LE strip test seems to be a valuable additional tool in the diagnosis of pediatric septic arthritis. The LE strip test has the advantages of being inexpensive and simple, providing real-time results and having a perfect negative predictive value to rule out the diagnosis of septic arthritis.

LEVEL OF EVIDENCE

Level II-diagnostic.

Systematic Review of Kingella kingae Musculoskeletal Infection in Children: Epidemiology, Impact and Management Strategies

Kingella kingae, a pathogen often responsible for musculoskeletal infections in children is the most common cause of septic arthritis and osteomyelitis in children 6 to 36 months of age. The aim of this study was to perform a systematic review of previous studies to determine the proportion of K. kingae in bacteriologically proven musculoskeletal infections among the pediatric population. A secondary objective was to describe the diagnostic strategies and outcome of patients with musculoskeletal infections caused by K. kingae. A systematic review was conducted to identify publications that report on musculoskeletal infections caused by K. kingae in the pediatric population (patients 0 to <18 years old with microbiologic culture and/or polymerase chain reaction (PCR) confirmation of K. kingae and a description of the musculoskeletal infection involved). Of 144 studies included in this review, we sought to determine the proportion of K. kingae pediatric musculoskeletal infections. A total of 711 (30.8%) out of 2308 pediatric cases with culture and/or PCR proven musculoskeletal infections had K. kingae successfully identified from twenty-nine studies. Of the 1070 patients who were aged less than 48 months, K. kingae was the organism identified in 47.6% of infections. We found the average age from the collated studies to be 17.73 months. Of 520 pediatric musculoskeletal patients in which K. kingae infections were identified and where the studies reported the sites of infection, a large proportion of cases (65%) were joint infections. This was followed by 18.4% osteoarticular infection (concomitant bone and joint involvement), with isolated bone and spine at 11.9% and 3.5%, respectively. Twenty-one papers reported clinical and laboratory findings in children with confirmed K. kingae infection. The median temperature reported at admission was 37.9°C and mean was 38.2°C. Fourteen studies reported on impact and treatment, with the majority of children experiencing good clinical outcome and function following antibiotic treatment with no serious orthopaedic sequelae.

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.

Kingella kingae as the Main Cause of Septic Arthritis: Importance of Molecular Diagnosis

BACKGROUND

Kingella kingae is an emergent pathogen causing septic arthritis (SA) in children.The objective of this study was to analyze the etiology of SA in children before and after the implementation of universal 16S rRNA gene polymerase chain reaction and sequencing (16SPCR) in synovial fluid.

METHODS

Children ≤14 years with acute SA from a Madrid cohort (2002-2013) were reviewed. Differences in etiology were analyzed before (period 1) and after (period 2) the implementation of bacterial 16SPCR in 2009. A comparison in epidemiology, clinical syndromes, therapy and outcome between infections caused by K. kingae and other bacteria was performed.

RESULTS

Bacteria were detected from 40/81 (49.4%) children, with a higher proportion of diagnosis after 16SPCR establishment (period 2, 63% vs. period 1, 31.4%; P = 0.005). The main etiologies were Staphylococcus aureus (37.5%) and K. kingae (35%), although K. kingae was the most common microorganism in P2 (48.3%). Children with K. kingae SA were less likely to be younger than 3 months (0 vs. 42.3%; P < 0.001), had less anemia (21.4 vs. 50%; P = 0.010), lower C-reactive protein (3.8 vs. 8.9 mg/dL; P = 0.039), less associated osteomyelitis (0 vs. 26.9%; P = 0.033), shorter intravenous therapy (6 vs. 15 days; P < 0.001), and had a nonsignificant lower rate of sequelae (0 vs. 30%; P = 0.15) than children with SA caused by other bacteria. However, they tended to have higher rate of fever (86 vs. 57%; P = 0.083).

CONCLUSIONS

K. kingae was frequently recovered in children with SA after the implementation of bacterial 16SPCR, producing a milder clinical syndrome and better outcome. Therefore, the use of molecular techniques may be important for the management of these children.

"Irritable Hip": Diagnosis in the Emergency Department. A Descriptive Study Over One Year

Background

A ‘limping child’ commonly presents to the emergency department (ED), often without a history of trauma. It is important that serious underlying pathology is ruled out before a diagnosis of benign irritable hip (IH). The aetiology of IH is not well understood and there may be geographical and seasonal variation. The aim of this study was to determine the basic epidemiology of IH in the Glasgow Population.

Methods

A retrospective analysis was carried out of all children discharged from the Glasgow Children’s Emergency Department from January to December 2016. Relevant discharge codes were determined and patient records screened. Any patient who did not have a discharge code had their presenting complaint and medical record screened.

Results

A total of 354 patients were diagnosed with IH, of which 319 and 189 were in the Greater Glasgow and Clyde and City of Glasgow catchment areas, respectively. The majority of these patients (n = 254) were diagnosed clinically. The incidence of IH was 177.7 per 100,000 children with a boy:girl ratio of 1.9:1 (209:110). The mean age of presentation was 3.5 years and the recurrence rate was 5.9% (n = 18). There was an increased incidence in spring (n = 111), especially in March (n = 42) and April (n = 40). There was no incidence variation or influence discernible by social deprivation.

Conclusion

In this population, IH has: (i) an atypical age profile (age distribution shift to younger), (ii) no marked association with social deprivation (in contrast to other studies), and (iii) a 'spring preponderance'. We suggest that most cases can safely be managed in the ED without recourse to further investigations or speciality referral.

Septic arthritis in children: diagnosis and treatment

Acute septic arthritis in children is usually hematogenous. It is more common in boys, and it most often affects the large joints of the lower limb. Diagnosis is based on cultures obtained from the infected joint and is supported by C-reactive protein blood test or ultrasound imaging. Staphylococcus aureus is the most common causative agent and is the primary target for empiric treatment. First-generation cephalosporins and clindamycin are suitable antibiotics. Vancomycin is utilized in areas with high rates of clindamycin- and methicillin-resistant S. aureus. After a short intravenous administration of 2–4 days, a total course of 2 weeks is sufficient in uncomplicated cases. Early antibiotic treatment has significantly improved the prognosis in high-income settings, but uncomplicated recovery is compromised if the treatment is delayed. Complications such as symptomatic osteoarthritis or avascular necrosis of the femoral head develop slowly. A long follow-up of 1–2 years is required to detect all possible sequelae.

Kingella kingae infections in children

BACKGROUND

Improvements in culture techniques and molecular detection methods have led to findings indicating that, particularly in infants and young children, Kingella kingae is a significantly more important pathogen than previously thought. However, despite this, the pediatric community is still largely unaware of the existence of this organism. The aim of this review is therefore to summarise current knowledge of the epidemiology, transmission, clinical presentation, diagnosis and treatment of K. kingae infections in children.

DISCUSSION

K. kingae is a common coloniser of the oropharynx, can be transmitted from child to child, and can cause outbreaks of infection. Invasive infections almost exclusively occur in children aged between six months and four years of age, and involve mainly joints and bone, less frequently the endocardium, and very rarely other localisations. With the exception of bacteremia and endocarditis, which can be followed by severe complications, the diseases due to K. kingae are usually accompanied by mild to moderate clinical signs and symptoms, and only slightly altered laboratory data. Moreover, they generally respond to widely used antibiotics, although resistant strains are reported. However, the mild symptoms and limited increase in the levels of acute phase reactants create problems because K. kingae disease may be confused with other clinical conditions that have a similar clinical picture.

CONCLUSIONS

Although K. kingae was identified more than 50 years ago, it is poorly known by pediatricians and is not systematically sought in laboratories. Education is therefore necessary in order to reduce the risk of outbreaks, permit the early identification of K. kingae infections, and allow the prompt prescription of adequate therapeutic regimens capable of avoiding the risk of a negative evolution in those cases in which this elusive pathogen can cause significant clinical problems.

Bacteremia in children: epidemiology, clinical diagnosis and antibiotic treatment

The diagnosis of bacteremia in children is important and it can be clinically challenging to recognize the signs and symptoms. The reported rates of bacteremia are higher in young children but with the increasing vaccine coverage, there has been a decrease in bacteremia due to the three vaccine preventable bacteria (Streptococcus pneumoniae, Haemophilus influenzae group b and Neisseria meningitidis). Notably, there have been increases in healthcare-associated bacteremias with a rise in Staphylococcus aureus and Gram negative bacteremias. This review provides a brief overview of the clinical diagnosis of bacteremia in children, focusing on the epidemiology, clinical characteristics, risk factors, antibiotic treatment, outcomes and preventative measures to reduce the incidence of bacteremia and improve morbidity and mortality.

Kingella kingae: carriage, transmission, and disease

Kingella kingae is a common etiology of pediatric bacteremia and the leading agent of osteomyelitis and septic arthritis in children aged 6 to 36 months. This Gram-negative bacterium is carried asymptomatically in the oropharynx and disseminates by close interpersonal contact. The colonized epithelium is the source of bloodstream invasion and dissemination to distant sites, and certain clones show significant association with bacteremia, osteoarthritis, or endocarditis. Kingella kingae produces an RTX (repeat-in-toxin) toxin with broad-spectrum cytotoxicity that probably facilitates mucosal colonization and persistence of the organism in the bloodstream and deep body tissues. With the exception of patients with endocardial involvement, children with K. kingae diseases often show only mild symptoms and signs, necessitating clinical acumen. The isolation of K. kingae on routine solid media is suboptimal, and detection of the bacterium is significantly improved by inoculating exudates into blood culture bottles and the use of PCR-based assays. The organism is generally susceptible to antibiotics that are administered to young patients with joint and bone infections. β-Lactamase production is clonal, and the local prevalence of β-lactamase-producing strains is variable. If adequately and promptly treated, invasive K. kingae infections with no endocardial involvement usually run a benign clinical course.