Kingella kingae: A type of bacteria that has emerged from obscurity to become known as an important cause of invasive infections in young children. These infections include especially septic arthritis (infection of joints), osteomyelitis (infection of bone), spondylodiscitis (infection of the spine and discs), bacteremia (infection of the bloodstream), and endocarditis (infection of the heart valves). Less frequently, Kingella kingae is responsible for lower respiratory tract infections and meningitis.
Kingella kingae is part of the bacterial flora of the pharynx (throat) in young children and is transmitted from child-to-child. The clinical presentation of disease due to Kingella kingae is often subtle so that making the diagnosis requires a high index of suspicion. A substantial fraction of children with invasive Kingella kingae infections have a recent history of stomatitis (inflammation within the mouth) or have had symptoms of an upper respiratory infection).
To compound the problem in making a diagnosis, the initial laboratory tests are frequently normal. The isolation and recognition of Kingella kingae in the laboratory need to take into account the fact that the organism is fastidious in its culture requirements. To optimize the chance of culturing Kingella kingae, the inoculation of fluid from infected joints into blood culture vials is strongly recommended.
Kingella kingae is susceptible to a wide array of antibiotics that are usually given empirically to young children including beta lactams. With the notable exception of cases of endocarditis (heart valve infection), the invasive infections caused by Kingella kingae usually run a benign clinical course.
Kingella kingae took the slow track to notoriety as an emerging pathogen. First isolated in 1960, it took until the 1990s for the bacterium to be recognised as a frequent cause of endocarditis and skeletal infections. It is thought that improved culture techniques, rather than epidemic spread of the organism, account for its rising recognition.
On a technical level, it might be mentioned that Kingella kingae is a member of the HACEK group of Gram-negative bacteria. The HACEK goup takes it name from its members, namely Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae. All these bacteria share the same fastidious culture requirements and, more importantly, they share the ability to infect the human heart valve.