Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Antimicrobial activity of commercial citrus-based natural extracts against Escherichia coli O157:H7 isolates and mutant strains

item Nannapaneni, R.
item Muthaiyan, A.
item Crandall, P.
item Johnson, M.g.
item O'bryan, C.a.
item Chalova, V.i.
item Callaway, Todd
item Carroll, J.a.
item Arthington, J.d.
item Nisbet, David - Dave
item Ricke, S.c.

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2008
Publication Date: 10/14/2008
Publication URL:
Citation: Nannapaneni, R., Muthaiyan, A., Crandall, P., Johnson, M., O'Bryan, C., Chalova, V., Callaway, T.R., Carroll, J., Arthington, J., Nisbet, D.J., Ricke, S. 2008. Antimicrobial activity of commercial citrus-based natural extracts against Escherichia coli O157:H7 isolates and mutant strains. Foodborne Pathogens and Disease. 5:695-699.

Interpretive Summary: In recent research it has been demonstrated that naturally occurring plant compounds such as volatile essential oils can kill harmful bacteria. Many of the bacteria-killing oils are found in citrus peels which can be purified to a high concentration and purity. These oils kill bacteria by mechanisms unlike antibiotics. Thus the concept of using these oils is both “green” and does not pose an increased risk of enhancing antibiotic resistance. In this study, seven citrus-derived essential oils were tested for their killing power of the pathogenic bacteria, E. coli O157:H7. Two very specific fractions of the purification process were found to inhibit the growth of E. coli O157:H7 in Petri dish assays. These results will allow us to focus on pursuing the most potent anti-pathogen oils for use in animals as part of an integrated pre-harvest pathogen reduction strategy.

Technical Abstract: Due to increasing concerns about the development of antimicrobial resistance amongst pathogenic bacteria, alternative strategies have been sought that do not use antibiotics to reduce pathogenic bacteria from foods and patients. A natural compound that has potent antimicrobial properties is citrus peel which contains a variety of essential oils that inhibit the growth of, or kill pathogenic bacteria. In the present study, seven citrus-based natural antimicrobials were evaluated for their ability to inhibit the growth of the pathogen E. coli O157:H7. Zones of inhibition of E. coli O157:H7 by the citrus-derived fraction (10 ul /6 mm disk) was determined by a disk-diffusion assay on Sorbitol-MacConkey agar. Inhibition zones were observed after 48 h lawn growth of E. coli O157:H7 cells at 37 deg C. Two citrus-based fractions, orange CP VAL terpeneless FAB 968611 and Limonene 1 x Dist FAB 955430 inhibited E. coli O157:H7 with inhibition zones of approx. 11-24 mm dia. The remaining other five citrus-derived extracts (orange oil FL VAL 1121 ARR 974760, Orange 5 x Conc VAL 4121 ARR 968374, orange terpenes ESS 1120 ARR 986259, orange terpenes CP 1100 ARR 986255, and orange terpenes OEO HP 1100 ARR 986257) were non inhibitory to E. coli O157:H7, yielding no clear inhibition zones. These studies show citrus-derived natural compounds differ in their inhibitory activity against E. coli O157:H7 and some have potential applications as inhibitory agents against E. coli O157:H7 in various pathogen reduction strategies.

Last Modified: 06/22/2017
Footer Content Back to Top of Page