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Antimicrobial Effects of Yarrow (Achillea millefolium) Essential Oil
Victoria A. RoyKimberly A. Hays, Ph.D.
Department of Natural ScienceDalton State College
Achillea millefolium• Herbaceous, perennial, flowering plant•Native to Asia, Europe and North America•Strong, sweet scent•Flowers May – June •Three color morphs
Yarrow History• Achilles– Soldiers wounds– Scientific name origin
• Native Americans – 46 tribes
• Algonquin• Lenape
– 28 ailments• Kidney disorders• Stomach disorders• Open wounds
• Greece– Military herb
Essential Oils: Growing Popularity
Objective
The objective of our study was to determine the antimicrobial effects of four commercially
purchased yarrow extracts against four common strains of bacteria.
Bacillus cereus
• Gram-positive• Rod shaped• Endospore forming• Pathology– Two types of food poisoning • Enteric and emetic
Escherichia coli
• Gram-negative• Rod-shaped • Found in lower intestine
of homoeothermic organisms• Opportunistic pathogen• Pathology– Food poisoning, urinary tract infections, neonatal
meningitis, Gram-negative pneumonia
Staphylococcus aureus
• Gram-positive • Coccal • Opportunistic pathogen• Found in normal skin flora • Pathology– MRSA– Staphylococcal scalded skin syndrome
• Produces toxins that cause blisters• Ritter’s disease
Pseudomonas aeruginosa
• Gram-negative • Rod-shaped• Opportunistic pathogen– Burn victims– Cystic fibrosis• Adheres to tissue surfaces• Replicates to infectious critical mass• Damage with virulence factors
Materials and Methods
• Kirby Bauer Disk Diffusion Susceptibility Test – 4 bacteria species• Confluent growth
– TSA agar– Impregnate paper disks with 15 μL of oil/water• DI Water control• Eden’s Garden (EOE)• Artisan Aromatics (EOA)• Nature’s Kiss (EOK)• Nature’s Oil (EON)
Photo: Misty Wheeler
Materials and Methods
• Kirby Bauer Disk Diffusion Susceptibility Test– Three replicates – 24 hour incubation at 37o C– Measure zones of inhibition if present
1
2
3 4
EON EOE EOA EOK Water0
2
4
6
8
10
12
B. cereusE. coliS. aureusP. aeruginosa
Treatment
Aver
age
Zone
of I
nhib
ition
(mm
)
Average Zone of Inhibition Per Treatment
Statistical Analyses
• Two-tailed T-tests (α < 0.05) were used to compare the average zones of inhibition between:– Oils vs. DI water control– Oils vs. oils
Results: B. cereus
EON – Natures’ OilEOE – Eden’s GardenEOA – Artisans AromaticsEOK – Nature’s Kiss
P values C EON EOE EOA EOKC EON 0.000043 EOE 0.00041 0.75 EOA 0.00019 0.00071 0.0049 EOK 0.00291 0.0202 0.011 0.14
EON EOE EOA EOK Water0
2
4
6
8
10
12
B. cereusE. coliS. aureusP. aeruginosa
Treatment
Aver
age
Zone
of I
nhib
ition
(mm
)
Average Zone of Inhibition Per Treatment
Results: E. coli
EON – Natures’ OilEOE – Eden’s GardenEOA – Artisans AromaticsEOK – Nature’s Kiss
P values C EON EOE EOA EOKC EON 0.000152 EOE 0.00026 0.81 EOA n/a 0.00015 0.00026 EOK n/a 0.00015 0.00026 n/a
EON EOE EOA EOK Water0
2
4
6
8
10
12
B. cereusE. coliS. aureusP. aeruginosa
Treatment
Aver
age
Zone
of I
nhib
ition
(mm
)
Average Zone of Inhibition Per Treatment
Results: S. aureus
EON – Natures’ OilEOE – Eden’s GardenEOA – Artisans AromaticsEOK – Nature’s Kiss
P value C EON EOE EOA EOKC EON 0.00024 EOE 0.00088 0.101 EOA n/a 0.00024 0.00088 EOK n/a 0.00024 0.00088 n/a
EON EOE EOA EOK Water0
2
4
6
8
10
12
B. cereusE. coliS. aureusP. aeruginosa
Treatment
Aver
age
Zone
of I
nhib
ition
(mm
)
Average Zone of Inhibition Per Treatment
Results: P. aeruginosa
EON – Natures’ OilEOE – Eden’s GardenEOA – Artisans AromaticsEOK – Nature’s Kiss
P value C EON EOE EOA EOKC EON n/a EOE n/a n/a EOA n/a n/a n/a EOK n/a n/a n/a n/a
Summary of Results
• All essential oils showed significant zones of inhibition on:– B. cereus
• Two essential oils (EOE and EON) had significant zones on inhibition on:– S. aureus (Mean = 10.21mm)– E. coli (Mean = 7.77mm)
• No measurable zones on inhibition on – P. aeruginosa
Discussion
• Potential cause for differences: – Gram interactions • B. cereus and S. aureus = Gram positive
– No outer membrane– More susceptible to antibiotics
• E. coli and P. aeruginosa = Gram negative– Purity of oils• Incorrect labeling and advertising
– Problems culturing P. aeruginosa • Passed plates did not grow
Future Directions
• Steam distillation– Requires large amounts of plant material– Small product of essential oil– Analysis of commercial and our oils
Future Directions
• Test more bacteria – Because B. cereus had the largest zones of
inhibition, move on to Bacillus anthracis (common in livestock and occasionally in humans)
Acknowledgements• Dr. April Kay• Dr. Richard Collison• Dr. Dean Turner• MaryAnn McBrayer• Misty Wheeler• Josh Peppers• Amanda Smith• Dr. Jonathan Fisher• DSC Foundation• DSC Vice President of Academic Affairs Office
Questions?
Photo: Misty Wheeler
