Antibacterial activity and mechanism of Cinnamomum loureirii bark oil against three foodborne and opportunistic pathogens.

This study investigated antibacterial effects of Cinnamomum loureirii essential oil (CLEO) against three foodborne microorganisms: Escherichia coli, Staphylococcus aureus, Pseudomonas putida. GC-MS showed trans-cinnamaldehyde was CLEO's major constituent (91.18%). CLEO's minimum inhibition concentrations (MICs) were 1, 0.25, 2 mg mL-1 for E.coli, S.aureus, P.putida, respectively. With rising CLEO concentration, nucleic acid and alkaline phosphatase (AKR) leakage of three bacteria increased gradually; S. aureus had higher leakage at 1/2MIC. This demonstrated CLEO disrupts cell wall/membrane integrity, affects cell structure, changes membrane permeability of bacterial proteins. Scanning/transmission electron microscopy (SEM/TEM) showed obvious bacterial morphological/ultrastructural changes, affecting normal cell division, further confirming CLEO-induced cell wall/membrane damage. Additionally, CLEO exhibited antibiofilm activity at sub-MIC levels, inhibiting three bacteria's biofilm formation. Under 2 × MIC, inhibition rates of E. coli, S. aureus, P. putida were 85.21%, 31.29%, 72.36%, respectively. Overall, CLEO is a promising natural antibacterial agent/multifunctional food additive for food and pharmaceutical industries.