Microbial Efflux Systems and Inhibitors: Approaches to Drug Discovery and the Challenge of Clinical Implementation

Fig. (2) Schematic illustration for: the mechanism of photodynamic inactivation including the Jablonski diagram (left) and the microbial permeability barriers of Gram-positive, Gram-negative bacteria and fungi (right). The PS initially absorbs a photon that excites it to the first excited singlet state and this can relax to the more long lived triplet state. This triplet PS can interact with molecular oxygen in two pathways, type I and type II, leading to the formation of reactive oxygen species (ROS) and singlet oxygen respectively.