In order to develop novel antistaphylococcal strategies, understanding the determinants of carriage and how humans respond to Staphylococcus aureus exposure is essential. Here, the primary S. aureus-specific humoral immune response and its association with nasal colonization was studied in young children. Sera from 57 colonized or non-colonized children, serially collected at birth and at 6, 14 and 24 months, were analysed for IgG, IgA and IgM binding to 19 staphylococcal proteins, using flow cytometry-based technology. The antibody responses showed extensive inter-individual variability. On average, the levels of antistaphylococcal IgA and IgM increased from birth until the age of 2 years (p <0.05), whereas the levels of IgG decreased (p <0.001). Placentally transferred maternal IgG did not protect against colonization. In colonized children, IgG and IgA levels for a number of proteins were higher than in non-colonized children. At both 14 and 24 months, the levels of IgG against chemotaxis inhibitory protein of S. aureus (at 24 months; median fluorescence intensity, 4928 vs. 24, p <0.05), extracellular fibrinogen-binding protein (987 vs. 604, p <0.05), and iron-responsive surface determinant H (62 vs. 5, p <0.05) were significantly higher in colonized children. The levels of IgA against CHIPS, IsdH and IsdA were higher (p <0.05). Therefore, CHIPS, Efb, IsdA and IsdH seem to play a role in nasal colonization of young children.

Serial nasal swabs were collected at the ages of 1.5, 6, and 14 months from 443 infants in the Generation R Study. The objective was to study the dynamics and determinants of Staphylococcus aureus nasal carriage in the first year of life. The prevalence of S. aureus carriage decreased in the first year of life, from 52.1% at the age of 1.5 months to 12.9% at 14 months. Persistent carriage, defined as continuous carriage of the same S. aureus strain at the three sampling moments, was rarely detected in early infancy.

To examine whether the timing of introduction of the allergenic foods cow's milk, hen's egg, peanuts, tree nuts, soy, and gluten is associated with eczema and wheezing in children 4 years of age or younger. Design: Population-based prospective cohort study from fetal life until young adulthood.

To study the association between Staphylococcus aureus nasal colonization and atopic dermatitis (AD) in infancy. Design: Population-based prospective cohort study of pregnant women and their children.