(160n) Antibacterial Mechanism of Thymol Against Enterobacter Sakazakii

Enterobacter sakazakii, an opportunistic foodborne Pathogen can arouse life-threatening infections in neonates, along with the clinical symptoms including necrotizing enterocolitis, bacteremia and meningitis. Due to the antibacterial effects against a variety of pathogenic bacteria, Thymol is the component of essential oils which can be extracted from plants such as Thymus, Ocimum, Origanum, etc. This study aims to uncover the antimicrobial activity of the thymol against E. sakazakii and its mechanism of action. The broth microdilution method was adopted to determine the minimum inhibitory concentration (MIC) of thymol.Becides, Membrane potential, intracellular ATP concentrations and intracellular pH (pHin) were measured and the antibacterial effect was observed by confocal laser scanning microscopy (CLSM) and field emission gun scanning electron microscope (FEGSEM), in order to elucidate a possible antibacterial mechanism. The MIC of thymol against E. sakazakii BNCC 186088 is 1.25 mg/ml, which inhibits the growth of E. sakazakii by breaking membrane integrity. Cell membrane depolarization, a reduction of intracellular ATP concentrations and pHin were observed after treatment, which showed that the cell membrane structures of E. sakazakii were apparently impaired by thymol, which means that thymol could destroy the integrity of the cell membrane of E. sakazakii, leading to the loss of cell homeostasis. The results indicate that thymol can be used as a food additive to prevent E. sakazakii contamination in food.