Pseudomonas aeruginosa is a leading cause of hospital-acquired infections for which the development of antibiotics is urgently needed. Unlike most enteric bacteria, P. aeruginosa lacks enzymes required to scavenge exogenous thymine. An appealing strategy to selectively target P. aeruginosa is to disrupt thymidine synthesis while providing exogenous thymine. However, known antibiotics that perturb thymidine synthesis are largely inactive against P. aeruginosa.

Here we characterize fluorofolin, a dihydrofolate reductase (DHFR) inhibitor derived from Irresistin-16, that exhibits significant activity against P. aeruginosa in culture and in a mouse thigh infection model. Fluorofolin is active against a wide range of clinical P. aeruginosa isolates resistant to known antibiotics. Metabolomics and in vitro assays using purified folA confirm that fluorofolin inhibits P. aeruginosa DHFR. Importantly, in the presence of thymine supplementation, fluorofolin activity is selective for P. aeruginosa. Resistance to fluorofolin can emerge through overexpression of the efflux pumps MexCD-OprJ and MexEF-OprN, but these mutants also decrease pathogenesis. Our findings demonstrate how understanding species-specific genetic differences can enable selective targeting of important pathogens while revealing trade-offs between resistance and pathogenesis.

铜绿假单胞菌是医院获得性感染的主要原因，迫切需要开发抗生素。与大多数肠道细菌不同，铜绿假单胞菌缺乏清除外源胸腺嘧啶所需的酶。选择性靶向铜绿假单胞菌的一个有吸引力的策略是破坏胸苷合成，同时提供外源胸腺嘧啶。然而，干扰胸苷合成的已知抗生素对于铜绿假单胞菌基本上没有活性。

在这里，我们表征了氟叶酸，一种源自 Irresistin-16 的二氢叶酸还原酶 (DHFR) 抑制剂，它在培养物和小鼠大腿感染模型中表现出显着的抗铜绿假单胞菌活性。氟洛林对多种对已知抗生素耐药的临床铜绿假单胞菌菌株具有活性。使用纯化的 folA 进行的代谢组学和体外测定证实，氟叶酸可抑制铜绿假单胞菌DHFR。重要的是，在补充胸腺嘧啶的情况下，氟福林活性对铜绿假单胞菌具有选择性。通过外排泵 MexCD-OprJ 和 MexEF-OprN 的过度表达可以出现对氟叶酸的抗性，但这些突变体也会降低发病机制。我们的研究结果表明，了解物种特异性遗传差异如何能够选择性地针对重要病原体，同时揭示耐药性和发病机制之间的权衡。