Parental Staphylococcus aureus carriage is associated with staphylococcal carriage in young children.

Background: Staphylococcus aureus colonization typically precedes infection but risk factors for colonization in children are not well defined. Our previous study suggested that S. aureus carriage in children is associated with parental carriage. Here we wished to distinguish the different components that play a role in the risk to a child of a S. aureus-carrying parent. Methods: Between 2002 and 2005, children (0-40 months) and their parents were screened for carriage of S. aureus and Streptococcus pneumoniae during I of 6 surveys. Data were collected from the parents and the medical files. Multivariate analysis of possible associated factors and effect modifiers was carried out. Pulse-field gel electrophoresis was performed to determine strain relatedness. Results: A total of 4648 children were screened. S. aureus was isolated from 342 (7.6%) children and 992 (22%) parents. Pairs of parent-child carriers were found in 155 cases, over twice the rate expected by chance (1.66%, P < 0.0001). The variable that was most significantly associated with carriage in children was having a parent carrier (OR: 3.35; 95% CI.2.59-4.33), whereas close contact with peers (as assessed by day care centers attendance or having young siblings) was not associated with carriage. Children <3 months had the highest carriage rate and children aged 6 to 12 months had the lowest (25.4% and 4.3%, respectively, P < 0.0001). Breast-feeding was not associated with higher or lower carriage. In 30 of 150 strains studied, >70% parent-child strains were genetically identical. Conclusions: Parental S. aureus colonization, but not DCC attendance or having young siblings, is an independent predictor for staphylococcal carriage in young children.