Exogenous adenosine counteracts tigecycline resistance in tet(X3)-harboring Escherichia coli

The rapid spread of antibiotic resistance poses a global health crisis. Tigecycline is a last-resort antibiotic, but the recent emergence of the plasmid-borne tet(X3) gene conferring high-level tigecycline resistance is deeply concerning. Here, we report a metabolomics-guided approach to overcome tet(X3)-mediated resistance. Using untargeted metabolomics, we identified adenosine as a key metabolic biomarker associated with tet(X3) expression. Remarkably, supplementation with exogenous adenosine was able to restore tigecycline susceptibility in tet(X3)-positive Escherichia coli both in vitro and in vivo. Our mechanistic investigations reveal that adenosine enhances the bactericidal effects of tigecycline by inducing oxidative stress, DNA/RNA damage, and cell membrane disruption in resistant bacteria. This study establishes a powerful metabolomics-driven strategy to potentiate antibiotic efficacy against drug-resistant pathogens. The adenosine-based adjuvant therapy represents a promising approach to combat the global crisis of antibiotic resistance.IMPORTANCEThe emergence and widespread dissemination of the high-level tigecycline resistance gene tet(X3) have posed a significant challenge to the efficacy of tigecycline, which serves as the "last line of defense" against antimicrobial-resistant bacteria. Although tigecycline has not been approved for veterinary clinical use, constant detection of tet(X3) genes and new subtypes in livestock farming environments poses a substantial threat to public health safety. While developing novel antibiotics is an effective approach to eradicate resistance genes/bacteria, it entails considerable costs and a lengthy timeframe. This study discovered that exogenous adenosine can effectively restore the sensitivity of tet(X3)-positive Escherichia coli to tigecycline through metabolic reprogramming based on a non-targeted metabolomics strategy. The findings are highly significant for exploring comprehensive mechanisms underlying bacterial multidrug resistance, utilizing metabolic reprogramming strategies to curb the spread of novel resistant genes, and treating clinical infections caused by tet(X3)-positive bacteria.