Kingella kingae

Kingella kingae
Scientific classification
Domain:	Bacteria
Phylum:	Proteobacteria
Class:	Betaproteobacteria
Order:	Neisseriales
Family:	Neisseriaceae
Genus:	Kingella
Species:	K. kingae
Binomial name
Kingella kingae Henriksen and Bøvre 1968

Kingella kingae is a species of Gram-negative aerobic coccobacilli. First isolated in 1960 by Elizabeth O. King, it was not recognized as a significant cause of infection in young children until the 1990s, when culture techniques had improved enough for it to be recognized. It is best known as a cause of septic arthritis, osteomyelitis, spondylodiscitis, bacteraemia, and endocarditis, and less frequently lower respiratory tract infections and meningitis.

There are four species of Kingella: K. kingae, the most common, is part of the bacterial flora of the throat in young children and is transmitted from child to child. When it causes disease, the clinical presentation is often subtle and preceded by a recent history of stomatitis or upper respiratory infection. Other species are K. indologenes, K. denitrificans (both causing endocarditis) and K. oralis found in dental plaque.

One notable exception is in cases of endocarditis (heart valve infection), which can be more refractory to treatment. K. kingae is the fifth member of the HACEK group of fastidious Gram-negative bacteria that cause endocarditis. Routine laboratory tests may be normal because the organism is difficult to culture. Inoculating the fluid from infected joints directly into blood culture vials can enhance the chances of an accurate culture, but extended culture times are not helpful.

The organism has also been known as Moraxella kingae.

K. kingae is oxidase-positive, catalase-negative, and beta-hemolytic.

Kingella kingae is thought to begin infection by colonizing the pharynx, crossing the epithelium by using an RTX toxin, and entering the circulation and reaching deeper tissues, such as bones and joints.

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