The antibacterial effect of Tanacetum argyrophyllum essential oil on kanamycin-resistant Escherichia coli by disruption of energy metabolism and proton fluxes

The essential oil (EO) of Tanacetum argyrophyllum harvested from Armenian flora (2080 m above sea level), characterized by a eucalyptol-camphor chemotype, and was investigated for its antibacterial activity, particularly against antibiotic-resistant bacterial strains. Chemical profiling revealed eucalyptol (35.0%), camphor (24.0%), and camphene (17.0%) as major constituents, alongside several minor terpenoids. The EO exhibited notable inhibitory effects against both wild-type Escherichia coli K-12 and kanamycin-resistant E. coli pARG-25 strains, with minimal inhibitory concentrations (MICs) reaching 100 µL/mL. . The combined influence of the EO with kanamycin could be described as synergistic, as Fractional Inhibitory Concentration Index (FICI) is 0.54. In this case the 62.5 µL/mL concentration of EO reduces the antibiotic MIC value fourfold. The investigation of colony-forming ability of bacteria under the influence of T. argyrophyllum EO revealed a reduction in bacterial viability by 30%. The changes in growth kinetics were also observed for both strains, which was indicated by a prolonged lag phase, suggesting impairment of early adaptation mechanisms. Further studies revealed that EO treatment significantly suppressed proton fluxes and ATPase activity in both strains. Particularly, total and DCCD-sensitive ATPase activities decreased by 1.5-fold, indicating a deviation in proton motive force maintenance and energy metabolism. The antibiotic-resistant E. coli pARG-25 strain exhibited higher ATPase activity compared to the wild-type, suggesting an elevated energy demand linked to resistance plasmid carriage, which was also targeted by the EO. These findings highlight that T. argyrophyllum EO disrupts bacterial energy homeostasis, representing a promising strategy for combating antibiotic-resistant pathogens. Overall, the results support the potential use of T. argyrophyllum EO as a natural antimicrobial agent.