The study shows that different Salmonella strains have varied surface sugars (LPS) that let them dodge the body’s immune cells and the natural antimicrobial peptide LL‑37. Changing these surface sugars makes the bacteria more vulnerable to LL‑37 and antibiotics like colistin.

S<i>almonella enterica</i> is comprised of over 2,500 serovars, in which non-typhoidal serovars (NTS), Enteritidis (SE), and Typhimurium (STM) are the most clinically associated with human infections. Although NTS have similar genetic elements to cause disease, phenotypic variation including differences in lipopolysaccharide (LPS) composition may control immune evasion. Here, we demonstrate that macrophage host defenses and LL-37 antimicrobial efficacy against SE and STM are substantially altered by LPS heterogeneity. We found that SE evades macrophage killing by inhibiting phagocytosis while STM survives better intracellularly post-phagocytosis. SE-infected macrophages failed to activate the inflammasomes and subsequently produced less interleukin-1&#x3b2; (IL-1&#x3b2;), IL-18, and interferon &#x3bb;. Inactivation of LPS biosynthesis genes altered LPS composition, and the SE LPS-altered mutants could no longer inhibit phagocytosis, inflammasome activation, and type II interferon signaling. In addition, SE and STM showed differential susceptibility to the antimicrobials LL-37 and colistin, and alteration of LPS structure substantially increased susceptibility to these molecules. Collectively, our findings highlight that modification of LPS composition by <i>Salmonella</i> increases resistance to host defenses and antibiotics.