Can early MRI distinguish between Kingella kingae and Gram-positive cocci in osteoarticular infections in young children?

Bacterial osteomyelitis in pediatric patients: a comprehensive review

Bacterial osteomyelitis, an inflammatory response in the bone caused by microorganisms, typically affects the metaphysis in the skeletally immature. Bacterial osteomyelitis possesses a significant diagnostic challenge in pediatric patients due to its nonspecific clinical presentation. Because the metaphysis is the primary focus of infection in skeletally immature patients, understanding the normal physiologic, maturation process of bones throughout childhood allows to understand the pathophysiology of osteomyelitis. Timely and accurate diagnosis is crucial to initiate appropriate treatment, and prevent long-term sequelae and efforts must be made to isolate the causative organism. The potential causative organism changes according to the age of the patient and underlying medical conditions. Staphylococcus Aureus is the most common isolated bacteria in pediatric pyogenic osteomyelitis whereas Kingella Kingae is the most common causative agent in children aged 6 months to 4 years. Imaging plays a pivotal role in the diagnosis, characterization, evaluation of complications, and follow up of bacterial osteomyelitis. Imaging also plays a pivotal role in the evaluation of potential neoplastic and non-neoplastic mimickers of osteomyelitis. In children, MRI is currently the gold standard imaging modality when suspecting bacterial osteomyelitis, whereas surgical intervention may be required in order to isolate the microorganism, treat complications, and exclude mimickers.

Kingella kingae Spinal Infections in Children

Nowadays, Kingella kingae is considered an important cause of primary spinal infections in children aged between 6 and 48 months. The presentation of the disease is often characterized by mild clinical features and a moderate biological inflammatory response, requiring a high index of suspicion. Performing magnetic resonance imaging (MRI) and obtaining an oropharyngeal specimen and subjecting it to a K. kingae-specific nucleic acid amplification test are recommended for its diagnosis. Most patients respond promptly to conservative treatment after administration of antibiotic therapy, which is prolonged for up to 3 months according to the individual clinical and biological response. Invasive surgical procedures are not required except for children who do not improve with antibiotic treatment, develop signs of cord compression, or if the presence of atypical microorganisms is suspected. Kingella kingae spinal infections usually run an indolent and benign clinical course, living no permanent sequelae.

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.

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.

Updates and Advances: Pediatric Musculoskeletal Infection Imaging Made Easier for Radiologists and Clinicians

Infants and children often present with a wide range of musculoskeletal (MSK) infections in daily clinical practice. This can vary from relatively benign superficial infections such as cellulitis to destructive osseous and articular infections and life-threatening deep soft tissue processes such as necrotizing fasciitis. Imaging evaluation plays an essential role for initial detection and follow-up evaluation of pediatric MSK infections. Therefore, a clear and up-to-date knowledge of imaging manifestations in MSK infections in infants and children is imperative for timely and accurate diagnosis that, in turn, can result in optimal patient management. This article reviews an up-to-date practical imaging techniques, the differences between pediatric and adult MSK infections, the spectrum of pediatric MSK infections, and mimics of pediatric MSK infections encountered in daily clinical practice by radiologists and clinicians.

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.

Imaging of Kingella kingae musculoskeletal infections in children: a series of 5 cases

PURPOSE

Kingella kingae musculoskeletal infections continue to be under-diagnosed and there remains a paucity of literature on its imaging features. The purpose of this manuscript is to review the imaging, clinical, and laboratory findings of microbiology-proven K. kingae infections.

MATERIALS AND METHODS

A retrospective review of musculoskeletal infections between January 1, 2013 and Dec 31, 2016 yielded 134 patients from whom 5 patients had confirmed K. kingae infections (3 boys and 2 girls, mean age of 16 months, range 9-38 months). Picture archiving and communication system and electronic medical records were reviewed.

RESULTS

At presentation, none of the patients had a fever and not all patients had abnormal inflammatory markers. Three patients had septic arthritis (2 knee and 1 sternomanubrial joints), one had epiphyseal osteomyelitis, and one had lumbar spondylodiscitis. The case of epiphyseal osteomyelitis of the distal humerus also had elbow joint involvement. A combination of radiography (n = 4), ultrasound (n = 2), and magnetic resonance (MR) imaging (n = 5) were performed. Prominent synovial thickening was observed for both knee and elbow joints and extensive regional myositis for all except for the patient with sternomanubrial joint infection. The diagnosis of K. kingae infection resulted in a change in the antibiotic regimen in 80% of the patients.

CONCLUSION

Disproportionate synovial thickening, prominent peri-articular myositis, and/or characteristic sites of involvement demonstrating imaging features of infection or inflammation in a young child with mild infectious symptoms and elevated inflammatory markers should invoke the possibility of an underlying K. kingae infection.

Kingella kingae-Associated Pediatric Osteoarticular Infections: An Overview of 566 Reported Cases

This study aimed to summarize clinical experience with Kingella kingae-associated pediatric osteoarticular infections (OAIs). We reviewed 566 cases in the English literature from 2000 to June 2014. More than 80% of the patients were diagnosed between 4 months and 4 years of age, and the male to female ratio was 1.14:1. The most frequent preceding illness was upper respiratory tract infections (82%). The top 3 OAIs types were septic arthritis (73.1%), osteomyelitis (15.7%), and spondylodiscitis (5.4%), and the most affected sites of these types were knee (46%), calcaneus (20%), and L4/5 disc (70%). All cases where polymerase chain reaction (PCR) technique was used were PCR positive, no reported cases of positive cultures for K kingae with negative PCR. The duration of antibiotics use ranged from 2 to 4 weeks. Beta-lactam antibiotics were the most frequently used intravenously and orally. The clinical efficacy was favorable.

MRI of acute osteomyelitis in long bones of children: Pathophysiology study

INTRODUCTION

The classic pathophysiology of acute osteomyelitis in children described by Trueta has a metaphyseal infection as the starting point. This hypothesis was recently brought into question by Labbé's study, which suggested a periosteal origin. Thus, we wanted to study this disease's pathophysiology through early MRI examinations and to look for prognostic factors based on abnormal findings.

MATERIAL AND METHODS

This was a prospective, multicentre study that included cases of long bone osteomyelitis in children who underwent an MRI examination within 7days of the start of symptoms and within 24hours of the initiation of antibiotic therapy. We also collected clinical, laboratory and treatment-related data.

RESULTS

Twenty patients were included, including one with a bifocal condition. The lower limb was involved in most cases (19/21). Staphylococcus aureus was found most frequently. Metaphyseal involvement was present in all cases. No isolated periosteal involvement was found in any of the cases. No prognostic factors were identified based on the various abnormal findings on MRI.

CONCLUSION

Our study supports the metaphyseal origin of acute osteomyelitis in children.

LEVEL OF EVIDENCE

II.

Unusual case of paediatric septic arthritis of the lumbar facet joints due to Kingella kingae

A 32-month-old boy presented with febrile limping that had developed over 6days, associated with right lumbosacral inflammatory swelling. Magnetic resonance imaging (MRI) showed joint effusion of the right L5-S1 zygapophyseal joint, complicated by destructive osteomyelitis of the L5 articular process and paraspinal abscess. Surgery was decided to evacuate the fluid accumulation and rule out differential diagnoses. The diagnosis of septic arthritis of the facet joint was confirmed intraoperatively; real-time quantitative PCR analysis identified Kingella kingae. This is the first substantiated paediatric case of zygapophyseal joint septic arthritis due to K. kingae. K. kingae is the most common pathogen responsible for invasive osteoarticular infection in children under 4years of age. Since empiric antibiotics are effective in early stages, physicians should consider the possibility of spinal infections due to K. kingae when a limping child under 4years of age presents with a fever.

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.

Two atypical cases of Kingella kingae invasive infection with concomitant human rhinovirus infection

We describe two atypical cases of Kingella kingae infection in children diagnosed by PCR, one case involving a soft tissue abscess and one case a femoral Brodie abscess. Both patients had concomitant human rhinovirus infection. K. kingae strains, isolated from an oropharyngeal swab, were characterized by multilocus sequence typing and rtxA sequencing.

Osteomyelitis and beyond

Musculoskeletal infections are a cause of considerable morbidity in children. Symptoms and signs are often nonspecific, and imaging is needed to define the anatomical location of infected tissue or fluid collections for diagnostic aspiration or biopsy. Prompt diagnosis and precise localization of the infection site has become even more imperative with the emergence and dissemination of highly invasive organisms such as community-acquired Staphylococcus aureus. Although radiography, bone scintigraphy and US continue to play a role, MRI is now the preferred imaging modality for definitive evaluation of pediatric musculoskeletal infections because of its capability of simultaneously assessing the osseous, articular and muscular structures without ionizing radiation exposure. This article focuses on the imaging characteristics of osteomyelitis, septic arthritis and pyomyositis and the differentiating features of potential mimics of infection.

30 years of study of Kingella kingae: post tenebras, lux

Kingella kingae is a Gram-negative bacterium that is today recognized as the major cause of joint and bone infections in young children. This microorganism is a member of the normal flora of the oropharynx, and the carriage rate among children under 4 years of age is approximately 10%. K. kingae is transmitted from child to child through close personal contact. Key virulence factors of K. kingae include expression of type IV pili, Knh-mediated adhesive activity and production of a potent RTX toxin. The clinical presentation of K. kingae invasive infection is often subtle and may be associated to mild-to-moderate biologic inflammatory responses, highlighting the importance a high index of suspicion. Molecular diagnosis of K. kingae infections by nucleic acid amplification techniques enables identification of this fastidious microorganism. Invasive infections typically respond favorably to medical treatment, with the exception of cases of endocarditis, which may require urgent valve replacement.