Three cases of Kingella kingae infection in young children

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.

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.

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.

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.

Detection of Kingella kingae osteoarticular infections in children by oropharyngeal swab PCR

OBJECTIVE

The purpose of this study was to investigate if oropharyngeal swab polymerase chain reaction (PCR) could predict osteoarticular infection (OAI) due to Kingella kingae in young children.

METHODS

One hundred twenty-three consecutive children aged 6 to 48 months presenting with atraumatic osteoarticular complaints were prospectively studied. All had a clinical evaluation, imaging, and blood samples. Blood and oropharyngeal specimens were tested with a PCR assay specific for K kingae. OAI was defined as bone, joint, or blood detection of pathogenic bacteria, or MRI consistent with infection in the absence of positive microbiology. K kingae OAI was defined by blood, bone, or synovial fluid positivity for the organism by culture or PCR.

RESULTS

Forty children met the OAI case definition; 30 had K kingae OAI, 1 had another organism, and 9 had no microbiologic diagnosis. All 30 oropharyngeal swabs from the K kingae case patients and 8 swabs from the 84 patients without OAI or with OAI caused by another organism were positive. The sensitivity and specificity of the oropharyngeal swab PCR assay for K kingae were 100% and 90.5%, respectively.

CONCLUSIONS

Detection of K kingae DNA in oropharyngeal swabs of children with clinical findings of OAI is predictive of K kingae OAI. If these findings are replicated in other settings, detection of K kingae by oropharyngeal swab PCR could improve the recognition of OAI.

Molecular diagnosis of Kingella kingae osteoarticular infections by specific real-time PCR assay

Kingella kingae is an emerging pathogen that is recognized as a causative agent of septic arthritis and osteomyelitis, primarily in infants and children. The bacterium is best detected by rapid inoculation in blood culture systems or by real-time PCR assays. Pathogenesis of the agent was linked recently to the production of a potent cytotoxin, known as RTX, which is toxic to a variety of human cell types. The locus encoding the RTX toxin is thought to be a putative virulence factor, and is, apparently, essential for inducing cytotoxic effects on respiratory epithelial, synovial and macrophage-like cells. Herein, we describe a novel real-time PCR assay that targets the RTX toxin gene and illustrate its use in two clinical cases. The assay exhibited a sensitivity of 30 c.f.u., which is 10-fold more sensitive than a previously published semi-nested broad-range 16S rRNA gene PCR, and showed no cross-reactivity with several related species and common osteoarticular pathogens.

Kingella kingae: from medical rarity to an emerging paediatric pathogen

In recent years, Kingella kingae has emerged as an important cause of invasive infections in young children, especially septic arthritis, osteomyelitis, spondylodiscitis, bacteraemia, and endocarditis, and less frequently lower respiratory tract infections and meningitis. The organism is part of the pharyngeal flora of young children and is transmitted from child-to-child. The clinical presentation of invasive K kingae disease is often subtle and laboratory tests are frequently normal. A substantial fraction of children with invasive K kingae infections have a recent history of stomatitis or symptoms of upper-respiratory-tract infection. The organism is susceptible to a wide array of antibiotics that are usually given empirically to young children including beta lactams, and with the exception of cases of endocarditis, the disease runs a benign clinical course. Although isolation and recognition of the organism is not difficult, clinicians and microbiologists should be aware of its fastidious nature. To optimise the recovery of K kingae, inoculation of synovial fluid specimens into blood culture vials is strongly recommended.