Legionella pneumophila is distinguished by an O-antigen composition rich in Legionaminic acid [299], a nonulosonic sugar (nine-carbon backbone). Although named after L. pneumophila, Legionaminic acid is also found in Campylobacter and Acinetobacter species . In Acinetobacter, Legionaminic acid has been linked to virulence and MDR [300]. This sugar is critical for the integrity of LPS [299], but its direct contribution to AMP resistance remains unclear. Legionaminic acid effectively suppresses immune responses by mimicking eukaryotic sialic acid, a strategy employed by many bacterial species to avoid detection by the immune system . It is important to note that immune-evading LPS modifications do not fully protect against endogenous AMPs, a component of innate immunity. Consequently, bacteria must evolve mechanisms to evade both the immune system and AMPs. For example, the LPS of Helicobacter pylori simultaneously exhibits AMP-resistant and immune-escaping features. Bacteria that cause chronic infections, such as H. pylori, are particularly adept at evading immune responses while withstanding the continuous presence of cationic AMPs in bodily fluids of mammals. This prolonged bacterial-AMP co-evolution has equipped bacteria with mechanisms to resist even last-resort antibiotics like polymyxins.