Abstract
Asymptomatic colonization by
Staphylococcus aureus is a precursor for infection, so identifying the mode and source of transmission which leads to colonization could help target interventions. Longitudinal studies have shown that some people are persistently colonized for years, while others seem to carry
S. aureus for weeks or less, and conventional wisdom attributes this disparity to an underlying risk factor in the persistently colonized. We analyze published data with mathematical models of acquisition and carriage to compare this hypothesis with alternatives. The null model assumes a homogeneous population and still produces highly variable colonization durations (mean of 1.94 years, 5
th percentile 0.1 years, 95
th percentile 5.8 years). Simulations show that this inherent variability, combined with censoring in longitudinal cohort studies, i s sufficient to produce the appearance of "persistent carriers," "intermittent carriers," and "noncarriers" in data. Our estimates for colonization duration exhibit sensitivity to the assumption that false positives can occur despite being rare, but our model-based approach simultaneously estimates specificity and sensitivity along with epidemiological parameters. Our results show it is plausible that
S. aureus colonizes people indiscriminately, and improved understanding of the types of exposures which result in colonization is essential.
