# E. coli "super-contaminates" narrow ducts fostered by broad run-time distribution

## TL;DR

This study reveals how E. coli bacteria can rapidly travel upstream in narrow ducts, driven by broad run-time distributions, leading to fast contamination and potential medical emergencies.

## Contribution

It introduces a stochastic model linking bacterial run times to surface interactions, highlighting the importance of broad run-time distributions in upstream bacterial transport.

## Key findings

- E. coli can travel 15 mm upstream in 15 minutes.
- Broad run-time distributions are necessary to model contamination profiles.
- Standard exponential run-time models fail to reproduce experimental data.

## Abstract

One striking feature of bacterial motion is their ability to swim upstream along corners and crevices, by leveraging hydrodynamic interactions. This motion through anatomic ducts or medical devices might be at the origin of serious infections. However, it remains unclear how bacteria can maintain persistent upstream motion while exhibiting run-and-tumble dynamics. Here we demonstrate that E. coli can travel upstream in microfluidic devices over distances of 15 millimeters in times as short as 15 minutes. Using a stochastic model relating the run times to the time bacteria spend on surfaces, we quantitatively reproduce the evolution of the contamination profiles when considering a broad distribution of run times. Interestingly, the experimental data cannot be reproduced using the usually accepted exponential distribution of run times. Our study demonstrates that the run-and-tumble statistics determine macroscopic bacterial transport properties. This effect, that we name "super-contamination", could explain the fast onset of some life-threatening medical emergencies.