Abstract Shigella flexneri is the leading cause of bacillary dysentery (bloody diarrhea) with 165 million cases per year worldwide, including 1 million deaths. There is no vaccine currently available and the isolation of multiple antibiotic resistant strains from patients worldwide is becoming the norm. S. flexneri pathogenesis relies on the colonization of the human colon where the pathogen invades epithelial cells and spreads directly from cell to cell through actin-based motility. Using an infant rabbit model of human shigellosis recently developed by our group, we have discovered that the severity of the symptoms observed during bacillary dysentery, including bloody diarrhea and destruction of the intestinal mucosa, correlates with the efficiency of S. flexneri dissemination through cell-to-cell spread. Targeting the cellular pathways supporting S. flexneri dissemination therefore represents a potential medical countermeasure for bacillary dysentery. Here, we propose to discover small molecules that inhibit S. flexneri dissemination (Aim 1) and to prioritize the hit set based on chemical and biological triage (Aim 2) and limited and exploratory medicinal chemistry (Aim 3).

Various intracellular pathogens have evolved the ability to manipulate host cell processes in order to disseminate from infected cells to adjacent cells. In this proposal, we present our plans to identify small molecules that inhibit the cellular processes supporting the dissemination of Shigella flexneri, the agent of bacillary dysentery in humans (bloody diarrhea). The proposed approach will contribute to our general understanding of the mechanisms underlying microbial pathogenesis and constitute the foundation for the development of preventive and therapeutic interventions.