2025_Virulence_Supplementary Information.docx

<b>Abstract</b><i>Pseudomonas aeruginosa</i> is an opportunistic bacterium frequently infecting the lower airways of individuals with cystic fibrosis (iwCF). This study examines colistin (CST) resistance mechanisms in <i>Psa</i>-ST3351 and their effects on bacterial virulence. <i>Psa</i>-ST3351 represents a novel sequence type, CST-resistant isolate from a child with CF. We show that <i>Psa</i>-ST3351 CST-resistance requires the addition of 4-amino-4-deoxy-L-arabinose to lipid A. Surprisingly, CST-exposure induced a non-mucoid-to-mucoid transition characterized by enhanced swarming motility, decreased aminoglycoside susceptibility, impaired ExoS secretion via the type-3 secretion system, and increased bacterial competition, all hallmarks of a chronic infection phenotype. CST-treated <i>Psa</i>-ST3351 exhibited reduced phagocytosis by macrophages, although the induction of pro-inflammatory cytokines remained intact. Moreover, CST exposure enhanced the pathogenicity of <i>Psa</i>-ST3351 in a murine pneumonia model. We conclude that CST-mediated transition from a non-mucoid-to-mucoid phenotype in <i>Psa</i>-ST3351 may have implications, particularly when CST-resistance and mucoid conversion remain undetected in iwCF treated with nebulized CST.

摘要：铜绿假单胞菌（Pseudomonas aeruginosa）是一种机会致病性细菌，常可感染囊性纤维化（cystic fibrosis, CF，缩写iwCF）患者的下呼吸道。本研究聚焦铜绿假单胞菌序列型3351（Psa-ST3351）的黏菌素（colistin, CST）耐药机制及其对细菌毒力的影响。Psa-ST3351是从一名CF患儿体内分离得到的新型耐黏菌素菌株。研究表明，Psa-ST3351的黏菌素耐药性依赖于脂质A（lipid A）的4-氨基-4-脱氧-L-阿拉伯糖修饰。令人意外的是，黏菌素暴露可诱导非黏液型向黏液型表型转化，该转化具备以下特征：群集运动能力增强、氨基糖苷类药物敏感性下降、Ⅲ型分泌系统（type 3 secretion system）介导的ExoS蛋白分泌受损，以及细菌竞争能力提升——上述均为慢性感染表型的典型标志。经黏菌素处理的Psa-ST3351被巨噬细胞吞噬的能力降低，但其促炎细胞因子的诱导水平未受影响。此外，黏菌素暴露可增强Psa-ST3351在小鼠肺炎模型中的致病力。综上，黏菌素介导的Psa-ST3351非黏液型向黏液型表型转化或具有重要临床意义，尤其当接受雾化黏菌素治疗的CF患者体内未检出黏菌素耐药性与黏液型转化时，该现象的潜在影响更需重视。