Aromatogram (essential oils)

Sensitivity testing of vaginal microbes against essential oils. Is looked at with recurring vaginal infections.

What the aromatogram shows methodologically

For the aromatogram, microbes from the swab are cultured in the laboratory and isolated as a pure culture. Much as with an antibiogram, the microbe is then spread on a culture medium, and discs soaked in various essential oils are placed on it. After incubation, the zone of inhibition around each disc is measured – the area in which the microbe has not grown. A larger zone of inhibition means that the growth of this isolated microbe was inhibited more strongly by this oil under laboratory conditions. Other methods dilute the oils step by step and determine the concentration at which growth no longer occurs.

How essential oils act on microbes in the aromatogram

Essential oils are mixtures of many volatile substances, such as thymol and carvacrol from thyme, terpinen-4-ol from tea tree oil or linalool from lavender. These fat-soluble substances embed themselves in the cell membranes of bacteria and fungi and make them more permeable: ions and cell components leak out, the voltage across the membrane collapses, and membrane-bound enzymes work less well. How sensitively a microbe reacts differs between species and even between individual strains of the same species – which is why the aromatogram tests the isolated microbe itself.

What are the limits of the aromatogram?

The aromatogram is a laboratory finding on isolated microbes. On the mucosa, by contrast, microbes live in a mixed flora, often protected in biofilms, surrounded by mucus and alongside lactobacilli, which can also be inhibited by the same substances. Methodologically, the procedure is less standardised than the antibiogram: essential oils are volatile and barely water-soluble, spread unevenly in the culture medium, and their composition varies with plant, origin and batch. There are no fixed breakpoints as there are for antibiotics. Whether a zone of inhibition in the laboratory predicts an effect in humans has not been demonstrated in studies.

The interpretation is given in your report.