Work

Colistin-induced transition from non-mucoid to mucoid phenotype in resistant Pseudomonas aeruginosa ST3351

Year: 2025

Type: article

Abstract: Pseudomonas aeruginosa is an opportunistic pathogen frequently infecting the lower airways of individuals with cystic fibrosis (iwCF). We investigated colistin (CST) resistance mechanisms in P. aeruginosa ST3351 (Psa-ST3351) and their impact on bacterial virulence. Psa-ST3351, a novel CST-resistant sequence type, was isolated from a child with CF. We demonstrate that CST resistance in Psa-ST3351 depends on the addition of 4-amino-4-deoxy-L-arabinose to lipid A. Moreover, exposure to CST induced a non-mucoid-to-mucoid phenotypic switch characterized by enhanced swarming motility, decreased susceptibility to aminoglycosides, impaired ExoS secretion via the type-III secretion system, and increased bacterial competition, all hallmarks of a chronic infection phenotype. CST-treated Psa-ST3351 also exhibited reduced phagocytosis by macrophages, despite the induction of pro-inflammatory cytokines remaining unaffected, and enhanced the pathogenicity in a mouse pneumonia model. These findings suggest that CST-induced mucoid conversion in CST-resistant Psa-ST3351 May contribute to disease progression in iwCF, particularly when CST resistance and mucoid conversion remain undetected during CST nebulized therapy.

Source: Virulence

DOI: 10.1080/21505594.2025.2580097