Sunday, August 12, 2012


Sensitivity of pathogenic and commensal bacteria from the human colon to essential oils.

Sensitivity of pathogenic and commensal bacteria from the human colon to essential oils.

Aug 2012


Rowett Institute of Nutrition and Health;


The microbiota of the intestinal tract plays an important role in colonic health, mediating many effects of dietary components on colonic health and during enteric infections. In the context of increasing incidences of antibiotic resistance in gut bacteria, complementary therapies are required for the prevention and treatment of enteric infections. Here we report the potential application of essential oils (EO) and pure EO compounds to improve human gut health. Nerolidol, thymol, eugenol and geraniol inhibited growth of the pathogens, Escherichia coli O157:H7(VT-), Clostridium difficile DSM1296, C. perfringens DSM11780, Salmonella typhimurium 3530 and S. enteritidis S1400 at half maximal inhibitory concentrations (IC50) varying from 50 to 500 ppm. Most EO showed greater toxicity to pathogens than commensals. However, the beneficial commensal, Faecalibacterium prausnitzii, was sensitive to EO at similar or even lower concentrations than the pathogens. The EO showed dose-dependent effects on cell integrity, as measured using propidium iodide, of Gram-positive bacteria. These effects were not strongly correlated to growth inhibition, however, suggesting that cell membrane damage occurred but were not the primary cause of growth inhibition. Growth inhibition of Gram-negative bacteria, in contrast, occurred mostly without cell integrity loss. Principal component analysis showed clustering of responses according to bacterial species rather than to the identity of the EO, with the exception that responses to thymol and nerolidol clustered away from the other EO. In conclusion, the selective effects of some EO might have beneficial effects on gut health if selected carefully for effectiveness against different species.

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