Acinetobacter baumannii is a Gram-negative bacterium that causes severe public health threat. It was set priority number one on the World Health Organization priority list for research and development of new antibiotics and treatments. This bacterium causes up to 10% of all the Gram-negative nosocomial infections. This is the main source of community-acquired diseases. This bacterium is an opportunistic bacterium that induces disease on people with weakened immune system. A. baumannii harbors a growing number of antibiotic resistances and can survive on abiotic surfaces, such as hospitals settings, for extended periods. This makes it an important burden for health care centers. Nowadays, only a small number of non-modern reference strains, sometimes lab adapted, is used to study this microorganism. The aim of this master thesis was to compare a library of modern clinical isolates to the common reference strains and evaluate reference strains relevance in the study of A. baumannii infections. In order to compare reference strains and isolates, we made phenotypical clusters using different methods. Macrocolony morphologies and density gradients allowed us to make the phenotypic clusters. Galleria mellonella, a wax moth, larvae and Acanthamoeba castellanii infection models enabled us to study the virulence and resistance to phagocytosis. Finally, transmission electron microscopy (TEM), was used to visualize the capsule and the intracellular localization of A. baumannii in an amoeba host. Our results highlighted that the strain AB5075, harboring a thick capsule, was the best reference strain tested. Indeed, it exhibits the phenotypic responses that match with the majority of the modern clinical isolates responses whereas the other reference strains were often less representative.
Evaluation of the reponse of Acinetobacter Baumannii, a multidrug resistant bacterium, confronted to a predatory amoeba
Philippe, C. (Author). 16 Jan 2020
Student thesis: Master types › Master in biochemistry and molecular and cell biology Research focus