Outbreaks of Kingella kingae Infections in Daycare Facilities

During the past 3 decades, Western countries have reported a rising number of mothers entering the workforce and, consequently, a growing number of children receiving care outside the home. This trend has substantial public health consequences because the incidence of infectious diseases in general, and of those caused by respiratory pathogens in particular, has substantially increased among daycare center attendees. These organisms are usually spread within daycare centers by child-to-child transmission; they colonize the upper respiratory tract surfaces, from which they can disseminate to other attendees. From the upper airways, pathogens may invade adjacent structures, such as the lungs, middle ear, or nasal sinuses, and may penetrate into the bloodstream, causing invasive diseases. Most bacterial pathogens responsible for such infections are enclosed by polysaccharide capsules that protect them from phagocytosis and complementmediated killing, ensuring their persistence on the respiratory mucosa and survival in the bloodstream and deep body tissues. Maturation of the T-cell independent arm of the immune system in humans is delayed until the age of 2 to 4 years; thus, young children are prone to colonization and infection by encapsulated bacteria.