Study of Antibacterial Properties of Cinnamaldehyde against Aeromonas hydrophila

Antibacterial properties of cinnamaldehyde against Aeromonas hydrophila were assayed in this study. To investigate the action mechanisms of cinnamaldehyde against A. hydrophila, we examined the antibacterial activity, bacterial membrane permeability, and ultrastructure of A. hydrophila cells treated with cinnamaldehyde. The results showed that the minimum inhibitory concentration (MIC) value of cinnamaldehyde against A. hydrophila NJ-35 was found to be 0.039 mg/mL. The trends of the growth curve of A. hydrophila treated with different concentrations of cinnamaldehyde (from 1/4 MIC to 2 MIC) were different, and there was a significant difference in the growth curve of different groups of treatment. There were significant differences in the K+ concentration among all treatment groups from 1 h to 5 h after incubation compared with that of the control. The highest K+ concentration was observed in the 1 MIC group of cinnamaldehyde. The ultrastructure of A. hydrophila cells treated with cinnamaldehyde was destroyed, and the morphology changed. These results indicated that cinnamaldehyde could inhibit the growth of A. hydrophila, increase bacterial membrane permeability, and damage cell membrane integrity, resulting in leakage of the A. hydrophila cell contents.