Salmonella biofilm formation diminishes bacterial proliferation in the C. elegans intestine

Non-typhoidal Salmonella serovars are a significant global cause of foodborne infections, owing their transmission success to the formation of biofilms. While the role of these biofilms in Salmonella's persistence outside the host is well understood, their significance during infection remains elusive. In this study, we investigated the impact of Salmonella biofilm formation on host colonization and virulence using the nematode model Caenorhabditis elegans. This infection model enables us to isolate the effect of biofilm formation on gut colonization and proliferation, as no gut microbiome is present and Salmonella cannot invade the intestinal tissue of the nematode. We show that a biofilm-deficient ΔcsgD mutant enhances gut proliferation compared to the wild-type strain, while the pathogen's virulence, the host's immune signaling pathways, and host survival remain unaffected. Hence, our work suggests that biofilm formation does not significantly contribute to Salmonella infection in C. elegans. However, complementary assays in higher-order in vivo models are required to further characterize the role of biofilm formation during infection and to take into account the impact of biofilm formation on competition with gut microbiome and epithelial invasion.