SF6024 - Evaluation of Essential Oils as an Alternative to Dietary Antibiotics to Control Food-borne Pathogens in Livestock

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Researcher:

Joshua Gong, Food Research Program, Agriculture and Agri-Food Canada

Objectives:

1. To identify essential oils or their components that can inhibit the growth of Salmonella, Escherichia coli O157:H7, and E. coli with K88 pili, but not the beneficial gut flora in vitro.
   

2. To examine the effects of identified essential oils on Salmonella and E. coli K88, gut flora, gut health, and animal (pig) growth performance in vivo.

Expected Benefits:

• To provide an alternative means to control Salmonella and E. coli K88 in swine production. This could potentially reduce the reliance of the industry on dietary antibiotics, minimize the development of antibiotic resistance, and enhance Ontario food safety and quality.

Summary of Research Results:

The emergence of super bugs (drug resistant bacteria) and drug residues in food are the two major food safety and human health concerns associated with drug use in agricultural production. Due to drug resistance concerns, feeding low levels of antibiotics to livestock for enhancing their growth and production performance purposes is no longer regarded as a normal production practice as it was viewed in the past. In fact, this practice will completely be banned in EU countries starting January, 2006.

As a result, developing alternatives to antimicrobial growth promoters (AGPs) has become urgent and a priority for the livestock industry to reduce prophylactic use of antibiotics. This is what exactly a research team, consisting of researchers from Agriculture and Agri-Food Canada, University of Guelph, Public Health Agency of Canada and Ontario Ministry of Agriculture, Food and Rural Affairs, was doing over the past two and a half years. The team had investigated the potential of essential oils/compounds as alternatives to AGPs to be used in swine production. Following are the major findings.

Essential Oil/Compounds

In this study, sixty-six essential oils/compounds were tested for their ability to inhibit the growth of Salmonella Typhimurium DT104 and E. coli O157:H7. Sixteen out of 66 were found to have strong antimicrobial property. Among these sixteen oils/compounds that exhibited >=80% inhibition, nine were further studied for their antibacterial effects against S. Typhimurium DT104, E. coli O157:H7, and E. coli K88, the stability at pH 2.0, and the effect on the growth of beneficial gut bacteria. Most of the oils/compounds demonstrated high efficacy against the pathogens with little inhibition towards lactobacilli and bifidobacteria which are beneficial bacteria, the members of the normal microflora in pig guts. These oils/compounds were also tolerant to low pH indicating that they will be effective under a low pH animal gut environment.

Conclusion:

The study led the following conclusions:

1. Some essential oils/compounds can be developed into the substitutes for dietary antibiotics in controlling both human and swine bacterial pathogens, as they have demonstrated strong antimicrobial activity, tolerance to low pH, and selectivity towards bacterial pathogens over beneficial gut bacteria in our in vitro studies.

2. Pig diets are a significant factor limiting the antimicrobial activity of essential oils. An effective and practical delivery of essential oils to the animal guts is critical in maximizing the antimicrobial effect of the oils in vivo. Some emulsifiers have been shown to be able to stabilize essential oil solutions for their antimicrobial activity.

3. An essential oil compound has been identified to retain its antimicrobial activity in the presence of diets, in addition to its tolerance to low pH and selectivity against Salmonella Typhimurium DT104. Pig infection experiments have also demonstrated a promise of this oil compound for future application although further investigation is required to determine the level of treatment and other issues regarding field use.