Immune response and clinical severity are shaped by skin-adapted Staphylococcus aureus in chronically infected patients.

Despite the well-described association of skin lesions with Staphylococcus aureus, the distinct ability of clinical isolates to influence the local and systemic inflammatory response in a patient-specific manner is insufficiently characterized. In this study, we analyzed clinical recessive dystrophic epidermolysis bullosa (RDEB), which is characterized by wounds chronically colonized with S. aureus, to explore the relationship between inflammatory immune response and strain diversity. Children with RDEB (moderate phenotype, n = 5; severe phenotype, n = 10) and controls (n = 18) were enrolled in the study. Profiling of plasma proteins (n = 800), immune cells (n = 30 subsets and cytokine-producing cells), and cytokines (n = 38) identified a specific inflammatory signature in severe disease. Furthermore, patients with severe RDEB presented a high frequency of interleukin-17A+ (IL-17A+) cells among CD4+ and mucosal-associated invariant T (MAIT) lymphocytes. Positive S. aureus cultures from the skin of patients with RDEB allowed whole-genome sequencing of patient strains and assessment of primary keratinocyte immune response upon bacterial challenge. S. aureus secretome and conditioned medium from keratinocytes challenged with S. aureus strains from patients with severe but not from those with moderate RDEB promoted strong activation and a pro-IL-17 response in both CD4+ and MAIT cells. Our findings show that S. aureus strains isolated from patients with severe RDEB induce an IL-17-skewed immune response and pave the way for precision microbiology to explain and predict the highly variable virulence potential of bacterial clinical isolates.