To study the pathogenesis of Avian pathogenic E. coli septicaemia, two in vivo infection models were established at the IMT (“Septicaemia” and “Lung infection model”) for the following purposes: (a) Fundamental pathogenesis studies by means of identification of DNA sequences, coding pathogenically important gene products ( STM mutants; Site-directed specific mutants) (b) Development and testing of new vaccines on the basis of newly identified potential virulence associated gene products, in order to prevent infection in poultry (c) Determination of resistance among genetically different chicken lines, to develop new breeding strategies – aiming at a selection of more resistant animals – thereby reducing the infection rate over a long term process (FUGATO) (d) Comparative studies of APEC with human pathogenic E. coli isolates, to determine more accurately the possible zoonotic potential of these organisms.
With the establishment of two chicken infection models, the main point of entry (respiratory tract) of the pathogen, as well as the main symptoms of an APEC infection (Septicaemia) was accounted for. Even though both models use 5 week old adult chickens that are infected intratracheally, a major differences is the infection dose in the Lung infection model, which only leads to a local infection of the chicken lung, without entry of the bacteria into the bloodstream. In this specialized model, studies involving adhesion, colonization and invasion of the respiratory tract epithelium are carried out (Photo GFP-E. coli in Atrium). In the framework of the FUGATO project, the mechanism of innate immunity of the chicken is studied.
GFP-labelled APEC strain IMT5155 (green) 1h after infection of the Atrium (red) of a 5-Week old chicken lung
In the septicaemia model, an infection dose was selected for the reproduction of Colisepticaemia with characteristic infection symptoms. This model serves the purpose of determining differences in virulence abilities between APEC and human pathogenic E. coli strains (NMEC, UPEC), testing potentially attenuated APEC mutants and studying differences in resistance between chicken lines with respect to an APEC infection. The read-out system includes among others, histological studies of tissue material, more importantly a clinical score as well as observation of pathomorphological changes with the help of an organ score.