Evolutionary rescue theory, antibiotic resistance and the details of bacterial infection

When a population faces a novel (stressful) environment this may cause the population to decline. In such situations evolutionary rescue theoryaims to predict the probability that a population adapts to the new environment (rescue), instead of facing the otherwise inevitable extinction. Thus, evolutionary rescue theory has the potential to help us understand when to expect the evolution of antibiotic resistance in bacterial populations. Yet, current models of evolutionary rescue fail to account for the mechanisms deployed by bacteria to cope with stressful conditions (like the presence of antibiotics). Here we examine two such mechanisms using stochastic modelling. First we examine the effect of biofilm formation, which occurs in the majority of bacterial infections. Biofilms have an explicit spatial structure, whilst standard evolutionary rescue theory assumes well-mixed populations. Secondly we examine the influence of persistercells, these are dormant cells that tolerate antibiotics exposure, which are also not modeled in standard evolutionary rescue theory.