5-ethyl-2'-deoxyuridine fragilizes Klebsiella pneumoniae outer wall and facilitates intracellular killing by phagocytic cells

Klebsiella pneumoniae is the causative agent of a variety of severe infections. Many K. pneumoniae strains are resistant to multiple antibiotics, and this situation creates a need for new antibacterial molecules. K. pneumoniae pathogenicity relies largely on its ability to escape phagocytosis and intracellular killing by phagocytic cells. Interfering with these escape mechanisms may allow to decrease bacterial virulence and to combat infections. In this study, we used Dictyostelium discoideum as a model phagocyte to screen a collection of 1,099 chemical compounds. Phg1A KO D. discoideum cells cannot feed upon K. pneumoniae bacteria, unless bacteria bear mutations decreasing their virulence. We identified 3 non-antibiotic compounds that restored growth of phg1A KO cells on K. pneumoniae, and we characterized the mode of action of one of them, 5-ethyl-2'-deoxyuridine (K2). K2-treated bacteria were more rapidly killed in D. discoideum phagosomes than non-treated bacteria. They were more sensitive to polymyxin and their outer membrane was more accessible to a hydrophobic fluorescent probe. These results suggest that K2 acts by rendering the membrane of K. pneumoniae accessible to antibacterial effectors. K2 was effective on three different K. pneumoniae strains, and acted at concentrations as low as 3 μM. K2 has previously been used to treat viral infections but its precise molecular mechanism of action in K. pneumoniae remains to be determined

Chemical modulation of bacterial intracellular killing in Dictyostelium discoideum

Le but du projet de ma thèse était d'identifier des composés altérant les interactions se produisant entre D. discoideum et K. pneumoniae. Klebsiella pneumoniae provoque de graves infections bactériennes menaçant la santé publique. Beaucoup de ces infections sont difficiles à traiter en raison de leur résistance aux antibiotiques. À partir de criblages précédemment effectués, de potentiels nouveaux composés antivirulents contre K. pneumoniae ont été caractérisés en utilisant D. discoideum et des techniques d'imagerie de cellules vivantes basées principalement sur la fluorescence. L'utilisation de D. discoideum dans l'étude des interactions hôte-pathogène et plus particulièrement sur les bactéries K. pneumoniae, nous a permis de caractériser deux composés intéressants. L'un d'eux, K2, doit maintenant être testé sur des modèles mammifères pour son potentiel développement thérapeutique. Le mode d'action du deuxième composé, K14, devrait être étudié plus en avant chez D. discoideum afin de mieux comprendre ses effets sur les mécanismes de destruction intracellulaires