Risk factors for persistent Staphylococcus aureus nasal carriage in the community

Staphylococcus aureus is a major human pathogen and commensal of the nose and other body sites. S. aureus colonisation (carriage) increases the risk of infection, so identifying carriers is central to infection control; however, few studies have combined robust methods with sufficient statistical power to determine the risk factors for carriage. We recruited over 22,000 adults into the CARRIAGE cohort study, who each returned self-taken nasal swabs and a questionnaire weekly for three weeks. We show that in a multivariable analysis with correction for multiple testing that the only factors significantly associated with persistent S. aureus carriage were younger age (with carriage rates declining after 60), male sex, higher BMI, chronic skin conditions, and antibiotic use in the prior month. Many previously proposed factors, including smoking and livestock contact, were not significantly associated. Overall, we demonstrate that only a limited number of risk factors influence S. aureus colonisation