Autophagy Induction by a Small Molecule Inhibits Survival in Macrophages and Mice.

are natural bacterial pathogens of humans and animals that cause systemic infection or gastroenteritis. During systemic infection, generally reside within professional phagocytes, typically macrophages, whereas gastroenteritis is caused by infection of epithelial cells. We are only beginning to understand which host pathways contribute to survival in particular cell types. We therefore sought to identify compounds that perturb host interactions using a chemical genetics approach. We found one small molecule, D61, that reduces load in cell-line and primary macrophages but has no effect on growth in epithelial cells or rich medium. We determined that in macrophages D61 induces LC3II, a marker of the autophagy pathway, and promotes aggregation of LC3II near We found that D61 antibacterial activity depends on the VPS34 complex and on ATG5. D61 also reduced load in the spleens and livers of infected mice. Lastly, we demonstrate that D61 antibacterial activity in macrophages is synergistic with the antibiotic chloramphenicol, but that this synergy is largely independent of the known autophagy-stimulating activity of chloramphenicol. Thus, a small molecule has anti-bacterial activity specifically in macrophages and mice based on the promotion of bacterial degradation by autophagy. Autophagy is a conserved cellular response to metabolic stress and to invading pathogens. For many pathogens, including , autophagy can play a detrimental or beneficial role during infection depending on the cellular context. We combined chemical genetics with single cell analyses and murine infection to dissect host-pathogen interactions. We identified a small molecule that reduces bacterial load in macrophages by increasing autophagic flux. This compound also reduces bacterial colonization of tissues in infected mice. These observations demonstrate the potential therapeutic utility of stimulating autophagy in cells and animals to curb infection.