Figure 2. Multistability and hysteresis in a simple model of the intestinal microbiota. A: phase diagram showing the three possible stability regions.

Antibiotic-sensitive bacteria dominate when and antibiotic-tolerant bacteria dominate when and therefore these are regions of monostability. There is a region of bistability between the two regions where domination by either sensitives or tolerants is possible. B: schematic display of the hysteresis phenomenon explaining cases where antibiotic treatment produces altered microbiota (i.e. tolerants domination) that persists long after antibiotic cessation. C–F: mean density values obtained simulating the Langevin dynamics for a maximum time after an instantaneous change of the parameter (C and D) and (E and F). These averages are obtained over noise realizations. C, D and E, F show the antibiotic-tolerants or antibiotic-sensitives densities, respectively, as a function of the social interaction parameter () with or the antibiotic killing () with .