Population dynamics of nasal colonization. Population dynamics of nasal colonization. Five-day-old neonatal rats were inoculated with 107 (black circles) or 104 cfu (diamonds) of either S. pneumoniae, H. influenzae or S. aureus. The geometric mean bacteria density in the nasal epithelium of 4-16 rats at each time-point is plotted. Dashed line represents limit of detection. Error bars represent SE.