Number of colony forming units (CFU) in the intraluminal (gray) and extraluminal (black) surfaces along the length of the urinary catheter (a) and over time (b). For (a), each point represents the mean and standard error over all individuals for each axial location of the catheter (males had 4 distinct locations, females had 3 locations). For (b), points represent mean and standard error for each surface of each individual. Note that the y-axis is on a log scale. Lines indicate a significant or nearly significant relationship based on the parameter estimates from mixed model analysis; for P values see Table1. Note that the means depicted do not incorporate subject effects. Urinary catheters from 5 males and 3 females catheterized in a level 1 trauma center for 1 to 16 days.