The cost of chronicity: <i>Pseudomonas aeruginosa</i> ’s silent evolution in the urinary tract

More than a century after Koch's postulates defined the microbial causes of disease, Stanley Falkow reminded us that pathogenicity is not an intrinsic property but a contextual outcome of microbial adaptation. The recent study by C. Martin-Duval, S. Dahyot, I. Coquisart, B. Bernay, et al. (Microbiol Spectr 13:e00456-25, 2025, https://doi.org/10.1128/spectrum.00456-25) illustrates this concept. By combining genomic, phenotypic, and proteomic analyses of sequential urinary isolates, the authors show how <i>Pseudomonas aeruginosa</i> progressively abandons virulence traits while reinforcing metabolic resilience during urinary tract infections. This commentary discusses how these findings challenge classical views of pathogenic success, highlighting the "cost of chronicity" as an adaptive trade-off between acute infection and long-term colonization. The urinary tract thus emerges not as a battlefield, but as a niche of persistence for <i>P. aeruginosa</i>.