Fig. 5: Patterns of bacterial colonisation along the catheter differ for different infection scenarios.

The predicted bacterial abundance at different positions along the outside and luminal catheter surfaces is shown for timepoints 24 and 36 h after infection, for 4 different infection scenarios. For each infection scenario, predictions for the outside surface are given in the upper panel, in green, and for the luminal surface in the lower panel, in pink. Predictions for 24 h are shown as dashed lines while predictions for 36 h are shown as solid lines. Here, a distance of 0 mm corresponds to the part of the catheter that contacts the skin or drainage bag, and 40 mm corresponds to the part that contacts the bladder. All model parameters are as given in Table 1. The four infection scenarios that are modelled are: a The skin acts as a reservoir from which infection can spread. b The drainage bag becomes contaminated, and bacteria ascend the catheter lumen. c The catheter is inoculated uniformly at time of insertion. d Bacteria are already present in the bladder prior to insertion. Note that here we assume the catheter is the same length as the urethra; in reality, there is an additional length of catheter beyond the urethra that connects to the drainage bag, so we would expect infections ascending from the drainage bag to have somewhat longer establishment times than shown in b.