OREGANO ESSENTIAL OIL ANTIBACTERIAL EFFICACY AGAINST MULTIPLE E. COLI STRAINS

SUMMARY Trials were conducted in collaboration with a UKAS accredited microbiology laboratory in the UK, to determine the antibacterial efficacy of oregano essential oil (OEO) against multiple strains of Escherichia coli using the zone of inhibition, disk diffusion technique.

The results of these trials support that OEO has antibacterial efficacy against E. coli and can therefore be used to help reduce the risk of disease and minimise the negative impact on animal performance caused by E. coli challenge. 

BACKGROUND  Escherichia coli is a gram-negative bacteria causing colibacillosis, a common bacterial infection, in livestock. It is a natural inhabitant of the gut but will proliferate rapidly during times of stress and immunosuppression, causing morbidity and mortality. Antibiotics have been widely used to treat infections caused by E. coli, however increased use has led to the rapid spread of antimicrobial resistance (AMR). This trial was conducted as part of Anpario’s 4 R’s approach to antibiotic usage.   Orego-Stim (OS) contains 100% natural oregano essential oil (OEO) and has been shown to have antibacterial efficacy against other gram-negative pathogens implicated in important livestock diseases.

TRIAL DESIGN In vitro trials were conducted in collaboration with a UKAS accredited microbiology laboratory in the UK in 2022-2024, to determine the antibacterial efficacy of OEO against strains of E. coli using the zone of inhibition, disk diffusion technique. A bacterial inoculum level of 1 x 107 – 1 x 108 was obtained and streaked over the surface of a dried Mueller Hinton agar plate to ensure an even distribution. Three replicate plates were prepared, where each replicate consisted of using one drop of OEO added per 6mm Whatman filter disc. These were incubated aerobically for 24 hours. Zone of inhibition was characterised as the area without bacterial growth and was measured using digital callipers. A large zone of inhibition would suggest a product is effective at inhibiting bacterial replication in the conditions tested.  

Figure 1: Antibacterial efficacy of OEO against strains of E. coli measured by zone of inhibition. Photograph shows complete zone clearance. The results of these studies support that OEO has antibacterial efficacy against multiple strains of E. coli (figure 1).  Orego-Stim including OEO can therefore be used to help reduce the risk of disease and minimise the negative impact on animal performance caused by E. coli challenge.