Anticancer agent 5-fluorouracil reverses meropenem resistance in carbapenem-resistant Gram-negative pathogens.

• 5-Fluorouracil (5-FU), identified via high-throughput screening, is a potential meropenem adjuvant • 5-FU boosts meropenem against both metallo- (NDM and IMP) and serine (KPC and OXA) β-lactamase-producing bacteria. • 5-FU increased bacterial metabolism and inhibited bla NDM-5 expression to restore meropenem sensitivity. • Combining 5-FU with meropenem increased mouse survival rates to 83.3%, compared with 16.7% with meropenem alone. The global increasing incidence of clinical infections caused by carbapenem-resistant Gram-negative pathogens requires urgent and effective treatment strategies. Antibiotic adjuvants represent a promising approach to enhance the efficacy of meropenem against carbapenem-resistant bacteria. This study shows that the anticancer agent 5-fluorouracil (5-FU, 50 µM) significantly reduced the minimum inhibitory concentration of meropenem against bla NDM-5 positive Escherichia coli by 32-fold through cell-based high-throughput screening. Further pharmacological studies indicated that 5-FU exhibited potentiation effects on carbapenem antibiotics against 42 Gram-negative bacteria producing either metallo-β-lactamases (MBLs), such as NDM and IMP, or serine β-lactamases (Ser-BLs), like KPC and OXA. These bacteria included E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter spp. , 32 of which were obtained from human clinical samples. Mechanistic investigations revealed that 5-FU inhibited the transcription and expression of the bla NDM-5 gene. In addition, 5-FU combined with meropenem enhanced bacterial metabolism, and stimulated the production of reactive oxygen species (ROS), thereby rendering bacteria more susceptible to meropenem. In a mouse systemic infection model, 5-FU combined with meropenem reduced bacterial loads and effectively elevated the survival rate of 83.3%, compared with 16.7% with meropenem monotherapy. Collectively, these findings indicate the potential of 5-FU as a novel meropenem adjuvant to improve treatment outcomes against infections caused by carbapenem-resistant bacteria. [Display omitted] [ABSTRACT FROM AUTHOR]