Respiratory Colonization by Kingella kingae, Person-to-Person Transmission, and Pathogenesis of Invasive Infection

Increasing recognition of Kingella kingae as an important pathogen of early childhood in recent years has elicited interest in the study of the asymptomatic carriage of the organism, its dissemination in the human population, and the role played by colonization of the upper respiratory tract in the pathogenesis of K. kingae invasion of the skeletal system and the endocardium. Research has revealed that K. kingae is a frequent component of the normal oropharyngeal microbiota, disclosed the subtle molecular mechanisms responsible for adherence of the bacterium to the pharyngeal mucosa, and revealed the presence of a potent RTX toxin, probably implicated in breaching the epithelial barrier, survival of the organism in the bloodstream, and damage to bone and joint tissues. Epidemiological studies have shown that carriage of K. kingae peaks in 6-30 month-old children, coinciding with the age of increased susceptibility to invasive disease, and daycare-center attendance represent a significant risk factor for pharyngeal colonization. The organism is transmitted from person-to- person by close contact between family members, playmaytes, and day-care center attendees. Carriage is characterized by frequent turnover of colonizing strains, similar to what has been described in other pathogens of respiratory origin.