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''Kingella kingae'' is a species of Gram-negative aerobic coccobacilli. First isolated in 1960, 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. ==Mechanism of infection== ''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. ''K. kingae'' expresses type IV pili, which allow for enhanced adhesion to respiratory epithelial and synovial cells and thus increased likelihood of colonization. These pili have also been shown to be reduced in number as pathogenesis progresses. σ54 regulates the transcription of pilA1, a major pilus subunit. PilS and PilR, regulatory transcription factors best known from the ''Pseudomonas aeruginosa'' pilus system, also may regulate pilA expression. High levels of type IV pili on ''K.kingae'' are associated with spreading/corroding colony types, while low levels of type IV pili are associated with nonspreading/noncorroding colony types of ''K. kingae''. The three different types of populations are: spreading/corroding (with high-density pilation), nonspreading/noncorroding colonies (low density pilation), and domed colonies (no pilation, and thus no adherence to epithelium). Generally, respiratory and nonendocarditis infections tend to be highly piliated, while joint fluid, bone, and endocarditis blood isolates are less piliated, if at all. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kingella kingae」の詳細全文を読む スポンサード リンク
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