How Oregano Oil Fights Harmful Bacteria and Their Toxins

Jenn Hoskins
19th July, 2024

How Oregano Oil Fights Harmful Bacteria and Their Toxins

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Northwest A&F University found that oregano essential oil (OEO) effectively reduces Listeria monocytogenes in food processing environments
  • OEO significantly lowers bacterial counts and biofilm formation, making it easier to eradicate L. monocytogenes from surfaces
  • OEO also decreases the hemolytic activity of L. monocytogenes, reducing the risk of human infections
Listeria monocytogenes (L. monocytogenes) is a significant foodborne pathogen known for its ability to form biofilms on utensil surfaces, which complicates its eradication in food processing environments. The presence of Listeriolysin O (LLO), a toxin responsible for hemolytic activity, further exacerbates the risk of human infections. A recent study conducted by researchers at Northwest A&F University investigated the inhibitory effects of oregano essential oil (OEO) on L. monocytogenes, focusing on its biofilm removal and hemolytic activity reduction[1]. The study found that the minimum inhibitory concentration (MIC) of OEO against L. monocytogenes was 0.03% (v/v). When L. monocytogenes was treated with OEO at 3/2 MIC for 30 minutes, the bacterial count dropped below the detection limit (10 CFU/mL) in both phosphate-buffered saline (PBS) and tryptic soy broth (TSB), starting from an initial load of about 6.5 log CFU/mL. In minced pork co-cultured with OEO at 15 MIC, the bacterial level was approximately 2.5 log CFU/g lower than in the untreated group. The mechanisms by which OEO inhibited L. monocytogenes included disruption of cellular morphology, increased levels of reactive oxygen species (ROS), enhanced lipid oxidation, hyperpolarization of membrane potential, and reduced intracellular ATP concentration. Additionally, OEO treatment reduced biofilm coverage on glass slides by 62.03% compared to the untreated group. Furthermore, OEO at 1/8 MIC decreased the hemolytic activity of L. monocytogenes to 24.6% of the positive control. Molecular docking suggested that components of OEO, such as carvacrol and thymol, might be responsible for reducing LLO activity. This study builds on previous research that explored various antimicrobial agents against L. monocytogenes. For instance, a combination of disinfectants with a bacteriophage cocktail was shown to significantly reduce L. monocytogenes populations and biofilm formation on food contact materials and foods[2]. However, regrowth of L. monocytogenes was observed on foods after five days, indicating the need for more effective long-term solutions. Thymol, a component of OEO, has previously been identified as effective against L. monocytogenes and Escherichia coli biofilms[3]. Thymol exhibited anti-biofilm activity at sub-MIC concentrations and significantly interfered with biofilm formation on stainless steel surfaces, simulating conditions in food processing environments. This aligns with the findings of the current study, which demonstrated OEO's efficacy in reducing biofilm coverage and hemolytic activity. The study also ties into research on antibiotic resistance, particularly in pathogens like Staphylococcus aureus. Eugenol, another essential oil component, has shown promise in combating vancomycin-resistant S. aureus by generating reactive oxygen species and causing membrane damage[4]. Similarly, OEO's ability to elevate ROS levels and disrupt cellular morphology in L. monocytogenes suggests a potential mechanism for its antimicrobial effects. Moreover, the study's findings on the morphological changes in L. monocytogenes due to OEO treatment resonate with previous research on the effects of alkaline stress on this pathogen. Exposure to high pH values induced significant changes in cell morphology, such as filamentation and chain formation, which were reversible under neutral conditions[5]. The perturbation of cellular morphology observed in the current study indicates that OEO may similarly stress L. monocytogenes cells, contributing to its antimicrobial action. In conclusion, the study by Northwest A&F University demonstrates that OEO is an effective natural antimicrobial agent against L. monocytogenes. By reducing biofilm formation, inhibiting hemolytic activity, and disrupting cellular mechanisms, OEO presents a promising solution for controlling this pathogen in food processing environments. The incorporation of findings from earlier studies underscores the potential of essential oils as viable alternatives to traditional disinfectants and antibiotics in combating foodborne pathogens.

HerbsMedicineBiochem

References

Main Study

1) Inhibitory effect and mechanism of oregano essential oil on Listeria monocytogenes cells, toxins and biofilms.

Published 16th July, 2024

https://doi.org/10.1016/j.micpath.2024.106801

Related Studies

2) Efficacy of disinfectant and bacteriophage mixture against planktonic and biofilm state of Listeria monocytogenes to control in the food industry.

https://doi.org/10.1016/j.ijfoodmicro.2024.110587

3) Control of Growth and Persistence of Listeria monocytogenes and β-Lactam-Resistant Escherichia coli by Thymol in Food Processing Settings.

https://doi.org/10.3390/molecules25020383

4) Eugenol Provokes ROS-Mediated Membrane Damage-Associated Antibacterial Activity Against Clinically Isolated Multidrug-Resistant Staphylococcus aureus Strains.

https://doi.org/10.4137/IDRT.S31741

5) Morphological changes in Listeria monocytogenes subjected to sublethal alkaline stress.

Journal: International journal of food microbiology, Issue: Vol 120, Issue 3, Dec 2007


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