A bacteriophage model based on CRISPR/Cas immune system in a chemostat

Stability analysis and persistence of a phage therapy model

This study deals with a phage therapy model involving nonlinear interactions of the bacteria-phage-innate immune response. The main aim of this work is to analytically and numerically examine the dynamic behavior of the phage therapy model. First, we investigate the positivity and boundedness of the system. Second, we analyze the existence and local asymptotic stability of different equilibrium solutions. Third, we investigate the global stability for equilibrium without immune system and equilibrium without phages, and coexistence equilibrium by means of the Bendixson-Dulac criterion and the Lyapunov functional method, respectively. Furthermore, we discuss the persistence and nonpersistence of the system under some conditions. Finally, we perform numerical simulations to substantiate the results obtained in this research.

DYNAMICS OF BACTERIA-PHAGE INTERACTIONS WITH IMMUNE RESPONSE IN A CHEMOSTAT

A mathematical model of bacteria-phage interaction in the chemostat is formulated, which incorporates the host immune response with an aim to mimic phage therapy in vivo. It is shown that the host immune response induces the backward bifurcation. Thus, there exists the bistability of phage-free equilibrium with the phage-infection equilibrium. More importantly, it is found that the model exhibits the coexistence of a stable phage-infection equilibrium with a stable periodic solution. The crucial implication of these phenomena is that phage infection fails both from the smaller dose of initial injection and from the larger dose of initial injection. Thus, a proper design of phage dose is necessary for phage therapy. Further analysis indicate that the inhibition effects of bacteria and phages can induce periodic oscillations and modulated oscillation.