The researchers utilized 18 different essential oils provided by a French manufacturer of essential oils Pranarôm Science. The researchers tested essential oils of cinnamon (Cinnamomum verum), lemongrass (Cymbopogon citratus), oregano (Origanum compactum), thyme (Thymus vulgaris – two species), Winter Savory (Satureja montana), clove (Eugenia caryophyllus), Palmarosa lemongrass (Cymbopogon martinii),camphor (Cinnamomum camphora – two species), peppermint (Mentha piperita), marjoram (Origanum marjorana), lavender (Lavandula stoechas), cajeput (Melaleuca cajuputi), tea tree (Melaleuca alternifolia), basil (Ocimum basilicum), Naiouli ea tree (Melaleuca quinquenervia), and rosemary (Rosmarinus officinalis).
The researchers extracted the bacteria Streptococcus pyogenes from the throat (pharynx) of a child who had tonsillitis. They incubated the bacteria and then tested each of the essential oils against it.
The researchers found 14 of the 18 essential oils had antibacterial activity against the Streptococcus pyogenes bacterial. Of these the cinnamon oil, the thyme oil, the lemongrass oil, the marjoram oil, and the Winter Savory oil had the greatest antibiotic activity against the tonsillitis bacteria S. pyogenes.
The zone of inhibition for these five oils with the most antibiotic potential ranged from 48 to 35 millimeters – the greater the zone of inhibition, the stronger the antibiotic potency.
Two other oils – clove oil and Palmarosa lemongrass oil – came in at 18 and 15 millimeters respectively. The remaining seven oils with antibiotic activity against the S. pyogenes ranged from 13 to nine millimeters zone of inhibition. They were camphor oil (CT linalool), peppermint oil, thyme oil (CT thujanol), marjoram oil, lavender oil, cajeput oil, and tea tree oil.
The obvious question is how this antibacterial activity, measured by inhibition zone, measures up against those of the most successful antibiotics. Well, a 2009 study published in the Journal of Bacteriology measured precisely that: The inhibition zones of the most popular antibiotics against Streptococcus pyogenes.
Zones of inhibition against S. pyogenes of Amoxicillin was 22.3 mm, Ampicillin 34.5 mm, Ampiciox 18.7 mm, Chloramphenicol 22.0 mm, Ciprofolxacin 30 mm, Erythromycin 14.5 mm, Fulcin 6.0 mm, Gentamicin 2.0 mm, Penicillin 39.0 mm, Rifampicin 27.0 mm, Septrin 19.0 mm, Tetracycline 10.5 mm, and Vancomycin 14.5 mm. The average zone of inhibition for the entire range of 13 antibiotics against S. pyogenes was 20.1, and as mentioned, the greatest was Penicillin at 39.
This compares to zones of inhibition between 48 mm and 35 mm for the cinnamon oil, the thyme oil, the lemongrass oil, the marjoram oil, and the Winter Savory oil.
And we must add to this that the 2009 study tested antibiotics that many species of bacteria – including some S. pyogenes – have since become more resistant to. During these past four years, many of these pharmaceutical antibiotics have lost some of their antibiotic potency against S. pyogenes and other bacteria.
The researchers noted that the essential oils’ antibiotic mechanisms varied, and ranged from their monoterpene content, aldehydes such as cinnamaldehyde (cinnamon), phenols such as thymol, carvacrol, eugenol and others, and many other compounds.
Other studies have also indicated some essential oils are significantly antibiotic. Thyme and lavender oils in particular have been found to have significant activity against some bacteria. In 2011, Moroccan researchers also found that two species of thyme essential oil were synergistic with antibiotic therapy.
Case Adams is a California naturopath who has authored 25 books on the science of natural healing together with numerous published online and print articles.
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