Bacteriophage-Resistant Salmonella rissen: An In Vitro Mitigated Inflammatory Response

Non-typhoid Salmonella (NTS) represents one of the major causes of foodborne diseases, which are made worse by the increasing emergence of antibiotic resistance. Thus, NTS are a significant and common public health concern. The purpose of this study is to investigate whether selection for phage-resistance alters bacterial phenotype, making this approach suitable for candidate vaccine preparation. We therefore compared two strains of Salmonella enterica serovar Rissen: R^R (the phage-resistant strain) and R^W (the phage-sensitive strain) in order to investigate a potential cost associated with the bacterium virulence. We tested the ability of both R^R and R^W to infect phagocytic and non-phagocytic cell lines, the activity of virulence factors associated with the main Type-3 secretory system (T3SS), as well as the canonic inflammatory mediators. The mutant R^R strain-compared to the wildtype R^W strain-induced in the host a weaker innate immune response. We suggest that the mitigated inflammatory response very likely is due to structural modifications of the lipopolysaccharide (LPS). Our results indicate that phage-resistance might be exploited as a means for the development of LPS-based antibacterial vaccines.