Eugenol eliminates carbapenem-resistant Klebsiella pneumoniae via reactive oxygen species mechanism

Multidrug-resistant (MDR) bacterial infections have gained increasing attention due to the high incidence rates and high mortality, especially for the carbapenem-resistant Klebsiella pneumoniae (CRKP) infection that can cause severe complications (e.g., pneumonia and sepsis) in multiple organs. Therefore, the development of new antibacterial agents against CRKP is imperative. Inspired by natural plant antibacterial agents with broad-spectrum antibacterial properties, the antibacterial/biofilm activity of eugenol (EG) on CRKP and their underlying mechanisms are investigated in our work. It is found that EG exhibits remarkable inhibitory effects on planktonic CRKP in a dose-dependent fashion. Meanwhile, the destruction of membrane integrity induced by the formation of reactive oxygen species (ROS) and glutathione reduction results in the leakage of bacterial cytoplasmic components, including DNA, β-galactosidase, and protein. Moreover, when EG contacts with bacterial biofilm, the whole thickness of the dense biofilm matrix decreases, and the integrity is destroyed. Overall, this work verified that EG could eliminate CRKP via ROS-induced membrane rupture, which offers vital evidence to explain the antibacterial ability of EG against CRKP.