Genome-Wide Screen Identifies Genes Required For Francisella Invasion In Non-Phagocytic Cells

The intracellular bacterium Francisella tularensis subspecies tularensis ( F. tularensis ) is the causative agent of tularemia, a disease that can result in 30–35% mortality if left untreated. Due to F. tularensis ' high infectivity and lethality the Centers for Disease Control and Prevention has classified it as a Biosafety Level 3 pathogen and a Category A Select agent. F. tularensis host cell invasion is crucial for their pathogenesis as without invasion disease does not occur. Upon entry into their host, the bacteria colonize both macrophages and epithelial cells. Despite significant research advances in macrophage infections, the study of epithelial infections has lagged behind. To investigate F. tularensis genes involved in epithelial cell invasion, we utilized a biosafety level 2 bacterial surrogate called F. tularensis subspecies novicida ( F. novicida ). A F. novicida transposon mutant library was screened to assess their invasion in hepatocytes. We selected for mutants with reduced intracellular growth using gentamycin‐based invasion/survival assays and confirmed our results microscopically using a subset of mutants. We discovered 232 mutants had significantly reduced invasion/survival levels as compared to wild type F. novicida infections. Ultimately our findings open a new door to the discovery of novel targets for the development of therapeutics and prophylactics. Grant Funding Source : CIHR and NSERC