An interesting note from a 2010 review of pathogenic E. coli by Croxen and Finlay in Nature Reviews Micro:

Intriguingly, EHEC can sense the hormones adrenaline and noradrenaline from host cells, as well as the quorum-sensing molecule auto-inducer 3 (AI-3) from gastrointestinal cells, to regulate motility and T3SS expression... Sensing of these molecules is required for virulence of EHEC in animal models and presents a new interaction that should be taken into account when considering pathogen–host interactions.

Some kind of a localization factor, perhaps, as adrenaline receptors are indeed present in the gastrointestinal tract.