Antibacterial mode of action of Cudrania tricuspidata fruit essential oil, affecting membrane permeability and surface characteristics of food-borne pathogens

Abstract

The present investigation reports on the chemical composition of Cudrania tricuspidata fruit essential oil (CTEO) and examines its possible antimicrobial mode of action against food-borne pathogenic bacteria. The CTEO was obtained by hydrodistillation of C. tricuspidata fruits using a microwave-assisted extraction technique. Gas chromatography-mass spectrometry analysis of the CTEO resulted in the determination of 29 different compounds, representing 94.46% of the total oil. The CTEO (1000 μg/disc) showed potential antibacterial effect as diameters of inhibition zones (15.0 ± 0.1–21.0 ± 1.0 mm) against the tested food-borne pathogenic bacteria including Bacillus cereus ATCC 13061, Staphylococcus aureus ATCC 12600, Listeria monocytogenes ATCC 7644, Salmonella typhimurium ATCC 43174 and Escherichia coli O157:H7 ATCC 43889. The minimum inhibitory (MIC) and minimum bactericidal (MBC) concentration values of CTEO against the tested bacteria were found in the range of 250–1000 μg/mL, respectively. Also the CTEO had potential inhibitory effect on the cell viability of the tested pathogens at MIC concentration. The SEM analysis showed the inhibitory effect of CTEO as confirmed by considerable morphological alterations on the cell wall B. cereus ATCC 13061 and E. coli O157:H7 ATCC 43889. In addition, the CTEO revealed its mode of action on membrane integrity as confirmed by release of extracellular ATP, loss of 260-nm absorbing materials and leakage of potassium ions against food-borne pathogenic bacteria. These findings suggest that CTEO showed a broad-spectrum of antibacterial efficacy and compromise its mode of action on membrane integrity.