Antibacterial mechanism of thymol against Enterobacter sakazakii

Thymol has a broad-spectrum antibacterial effect, but few studies have elucidated the antibacterial mechanism of thymol on Enterobacter sakazakii to date. This study aimed to uncover its antimicrobial mechanism against E. sakazakii. The minimum inhibitory concentration (MIC) of thymol was determined using the broth microdilution. Membrane potential, intracellular ATP concentrations, and intracellular pH (pHi) were measured, and the membrane damage was observed using a confocal laser scanning microscopy (CLSM) and a field emission gun scanning electron microscope (FEGSEM) to discuss the antibacterial effect of thymol. The MIC of thymol against E. sakazakii BNCC 186088 was 1.25 mg/mL. Cell membrane depolarization, decreased intracellular ATP concentrations, and lower pHi were observed after treatment with thymol, which indicates broken cell membranes and disrupted intracellular homeostasis. These results suggest that thymol has the potential to prevent bacterial contamination by E. sakazakii in the food industry.