Zebrafish as a model organism to study host-pathogen interactions

Zebrafish have been extensively used in biomedical research as a model to study vertebrate development but it is only recently that it has also been adopted into varied fields such as immunology and host-pathogen interactions. Zebrafish have a rapid life cycle, small size and the adults exhibit no territorial behavior in relatively dense cages. Under standard conditions each female lays an average of a hundred eggs per clutch, providing a large number of larvae per week. Their transparency during early life stages allows real time visualization of the different organs, which makes them especially suitable for the study of bacterial host-pathogen interactions. Traditionally, these studies have been technically challenging in higher organisms, given the loss of control over the bacteria once the pathogen infects its host. Here we describe an emerging approach to monitor Salmonella typhimurium infection progression using in vivo fluorescence upon parenteral infection. We have engineered Salmonella with the Cascade expression system; an efficient method to voluntarily activate bacterial heterologous gene expression at any point during infection once inside the Zebrafish macrophages, using a non-toxic inducer.