A High-Content, Phenotypic Screen Identifies Fluorouridine as an Inhibitor of Pyoverdine Biosynthesis and Pseudomonas aeruginosa Virulence

Pseudomonas aeruginosa is an opportunistic pathogen that causes severe health problems. Despite intensive investigation, many aspects of microbial virulence remain poorly understood. We used a high-throughput, high-content, whole-organism, phenotypic screen to identify small molecules that inhibit P. aeruginosa virulence in C. elegans. Approximately half of the hits were known antimicrobials. A large number of hits were non-antimicrobial bioactive compounds, including the cancer chemotherapeutic 5-fluorouracil. We determined that 5-fluorouracil both transiently inhibits bacterial growth and reduces pyoverdine biosynthesis. Pyoverdine is a siderophore that regulates the expression of several virulence determinants and is critical for pathogenesis in mammals. We show that 5-fluorouridine, a downstream metabolite of 5-fluorouracil, is responsible for inhibiting pyoverdine biosynthesis. We also show that 5-fluorouridine, in contrast to 5-fluorouracil, is a genuine anti-virulent compound, with no bacteriostatic or bacteriocidal activity. To our knowledge, this is the first report utilizing a whole-organism screen to identify novel compounds with antivirulent properties effective against P. aeruginosa.铜绿假单胞菌（Pseudomonas aeruginosa）是一种可引发严重健康问题的机会致病菌。尽管已开展大量深入研究，微生物毒力的诸多方面仍未得到充分阐明。本研究采用高通量、高内涵的全生物体表型筛选技术，旨在鉴定可在秀丽隐杆线虫（C. elegans）模型中抑制铜绿假单胞菌毒力的小分子化合物。筛选得到的命中化合物中约半数为已知抗菌剂，另有大量命中化合物属于非抗菌生物活性物质，其中包括癌症化疗药物5-氟尿嘧啶（5-fluorouracil）。研究证实，5-氟尿嘧啶可同时暂时性抑制细菌生长，并降低绿脓菌素（pyoverdine）的生物合成。绿脓菌素是一种铁载体，可调控多种毒力决定因子的表达，对哺乳动物的致病过程至关重要。进一步研究发现，5-氟尿嘧啶的下游代谢物5-氟尿苷（5-fluorouridine）正是抑制绿脓菌素生物合成的关键物质。此外，与5-氟尿嘧啶不同，5-氟尿苷是一种真正的抗毒力化合物，不具备抑菌或杀菌活性。据我们所知，本研究是首次利用全生物体筛选技术鉴定出对铜绿假单胞菌具有有效抗毒力特性的新型化合物的报道。