Kingella kingae: an emerging cause of invasive infections in young children.

Kingella kingae, a fastidious hemolytic gram-negative bacillus once considered to be an exceptional cause of disease, has emerged in recent years as an important invasive pathogen in children. When synovial fluid and other exudates were inoculated into blood culture bottles, enhanced recovery of the organism was observed, and an annual incidence of invasive K. kingae infections of 27.4 per 100,000 children younger than age 24 months was demonstrated in southern Israel. Skeletal infections are the most common clinical presentation of K. kingae, and studies conducted in that region have shown that this organism is the most common etiology of septic arthritis in children below the age of 24 months. Other invasive diseases caused by K. kingae include bacteremia, endocarditis, and infections involving the lower respiratory tract, the eyes, or the central nervous system. Recent studies have demonstrated that K. kingae is part of the normal oropharyngeal flora of young children. Clinical data suggest that the organism may gain access to the bloodstream in the course of an upper respiratory infection or stomatitis. The organism is susceptible to a wide range of antimicrobial drugs, and with the exception of some cases of endocarditis, K. kingae infections in children usually run a benign clinical course.