Assessment of the antimobial activity of olive leaf extract against foodborne bacterial pathogens

Authors: Liu, Yanhong; McKeever, Lindsay; Malik, Nasir

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2017
Publication Date: 2/2/2017
Citation: Liu, Y., McKeever, L., Malik, N.S. 2017. Assessment of the antimobial activity of olive leaf extract against foodborne bacterial pathogens. Frontiers in Microbiology. doi: 10.3389/fmicb.2017.00113.

Interpretive Summary: There is a need for novel methods to control pathogenic bacteria in the food supply. Olive leaf extract (OLE) is an herbal supplement that is beneficial to human health. It has antioxidant, as well as antimicrobial properties. Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Enteritidis are three major foodborne pathogens that cause serious human illness. In this work, OLE was shown to inhibit the growth of these three foodborne pathogens. Furthermore application of OLE also inhibited the movement of L. monocytogenes by abolishing the long hair-like cell surface structure known as a flagellum. Finally, OLE was found to inhibit the formation of L. monocytogenes and Salmonella biofilms (aggregate of microorganisms attached to a surface), which can be difficult to remove by commonly used sanitizers. Based on these findings, OLE has the potential to be used as a natural antimicrobial to control foodborne pathogens in food and the food environment.

Technical Abstract: Olive leaf extract (OLE) has been used traditionally as an herbal supplement since it contains polyphenolic compounds with beneficial properties ranging from increasing energy levels, lowering blood pressure, and supporting the cardiovascular and immune systems. In addition to the beneficial effects on human health, OLE also has antimicrobial properties. The aim of this work was to investigate the antimicrobial effect of OLE against major foodborne pathogens, including Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Enteritidis. Results demonstrated that at a concentration of 62.5 mg/ml, OLE completely inhibited the growth of these three pathogens. In addition, OLE also reduced cell motility in L. monocytogenes, which correlated with the absence of flagella as shown by scanning electron microscopy. Moreover, OLE inhibited biofilm formation in L. monocytogenes and S. Enteritidis. Taken together, OLE, a natural product, has the potential to be used as an antimicrobial to control foodborne pathogens.