Comparative metabolomics reveal key pathways associated with the synergistic activities of aztreonam and clavulanate combination against multidrug-resistant Escherichia coli

The use of combination antibiotics has been useful in the treatment of multidrug-resistant bacterial infections. The synergistic effect of amoxicillin/clavulanate and aztreonam combination against Escherichia coli carrying New Delhi metallo-β-lactamase (NDM) was primarily due to clavulanate inhibiting aztreonam degradation. In the present study, we employed metabolomic analysis to investigate the downstream changes in E. coli after treatment with aztreonam and clavulanate. E. coli metabolomes were compared at 1 and 24 h following treatments with clavulanate (4 µg/mL) and aztreonam (4 µg/mL) alone and in combination. Excluding false positives, 198 metabolites were identified to be affected by antibiotic treatment. Aztreonam/clavulanate combination inhibited cell wall synthesis more aggressively at 1 h and 24 h than aztreonam alone. The purine and pyrimidine metabolism, the central carbon metabolism, and the amino acid metabolism were also disrupted resulting in a prolonged bactericidal effect. This study reveals the synergistic killing mechanism of clavulanate and aztreonam combination against E. coli harboring NDM and provides a theoretical basis for the combined use of aztreonam/clavulanate in the treatment of multidrug-resistant E. coli infection. IMPORTANCE Multidrug-resistant Escherichia coli is a major threat to the health care system and is associated with poor outcomes in infected patients. The combined use of antibiotics has become an important treatment method for multidrug-resistant bacteria. However, the mechanism for their synergism has yet to be explored.