Spearmint Wipes Out Biofilms!
A new study tackles the topic of biofilms, the dangerous communities of bacteria that are wickedly difficult to eradicate.
Wikipedia explains that a “biofilm is any group of microorganisms in which cells stick to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS).”1
There is one thing that is vital to remember about biofilms. The antibiotic that will kill the bacteria that are floating as single cells in water are useless against biofilm. A researcher, Hongwei Yu, at the Center for Biofilm Engineering at Montana State University wrote:
. . . it has been discovered that within minutes of when a bacterium attaches to a surface it undergoes a remarkable change in gene function . . . as many as 40% of the genes of a bacterium may undergo up or down regulation in the transition from the planktonic to the biofilm state.2
This article also stated:
Many of the infections plaguing humans are actually caused by bacteria in the biofilm mode of growth, not the planktonic mode of growth. . . . traditional antibiotics have been tested on bacterial cells in their relatively unprotected, planktonic state. . . . the same bacterium is different in the biofilm state than in the planktonic state for which the antibiotic was designed and tested!3
The August 2015 study we are discussing for this week’s AIRASE research article is by six researchers from universities located in Tunisia and Italy.
What essential oil would you expect to be the star of this research? Cinnamon? Oregano? Thyme? Those oils are all known to be highly antibacterial. You may be as surprised as we were to find the essential oil they chose to go up against a virulent bacteria is none other than spearmint (Mentha spicata)! (Okay, the title gave it away, but aren’t you still a little surprised?)
The Centers for Disease Control didn’t have much good to say about the bacteria chosen for this study: Vibrio species. “Vibrios are gram-negative, rod-shaped bacteria that occur naturally in estuarine or marine environments. Roughly a dozen species are known to cause disease in humans, accounting for an estimated 80,000 illnesses, 500 hospitalizations and 100 deaths each year in the United States.”4 [See the CDC illustration below.]
This is a microscopic view of Vibrio, the rod-shaped bacteria that cause 80,000 illnesses and 100 deaths in the U.S. each year, often through contaminated seafood.
The researchers of our Tunisian and Italian study note that the genus Mentha has approximately 30 species that are cultivated from tropical to temperate climates in America, Europe, China, Brazil, India, Australia, and South Africa. The main species grown in temperate, Mediterranean, and subtropical regions are: M. arvensis (corn mint), M. x piperita L. (peppermint), M. citrata Ehrl. (bergamot mint), M. longifolia L. (wild mint), and M. spicata L. (spearmint).
Spearmint essential oil was not only tested against 30 Vibrio species (where it performed well) but perhaps more importantly for eradicating Vibrio biofilms on a polystyrene surface. The study’s authors report:
Our results showed that spearmint essential oil inhibited the tested Vibrio spp. strains’ biofilm production by 11.5% and 11.6% for V. alginolyticus ATCC 33787, and by 28% and 40% for V. vulnificus ATCC 27562 at 0.046 and 0.092 mg/mL, respectively. As regards to the Vibrio preformed biofilm disruption, the spearmint essential oil eradicated more than 50% of preformed biofilm V. cholerae ATCC 9459 and V. alginolyticus ATCC biofilms at 0.092 mg/mL.5
Incidentally, this study is one that can be downloaded at no charge: http://www.mdpi.com/1420-3049/20/8/14402 (then click on download).
A number of important conclusions came from this study:
The reported results obtained for Tunisian M. spicata essential oil (carvone/limonene chemotype) showed high antibacterial activity against Vibrio spp. as well as antioxidant properties. The low MIC and MBC values indicated that its use could consistently contribute to preserve seafood from the Vibrio proliferation that makes particularly hazardous the spreading worldwide habit of eating such foods raw or not well done.”6
The study continues:
Furthermore, the high antioxidant and anti-free radical activities registered could be important to preserve marine products known to contain a number of components prone to degradation. In particular, polyunsaturated fatty acids that quickly undergo peroxidation, generating as a primary product the peroxyl radicals could be efficiently scavenged by the M. spicata essential oil.
Therefore, such properties could be useful in prolonging seafood’s shelf life because they are protective against both microbiological and chemical deterioration, thus preventing loss of flavor and, most importantly, toxic agent formation. . . . it should be noted that, when ingested, M. spicata essential oil—due to its antioxidant, antiradical, and chelating properties—could contribute, with different mechanisms, to maintaining the balance of the organism’s redox state.
Hence, the use of M. spicata and its essential oil as a seafood seasoning could be useful in improving the seafood product’s taste, safety, and effect on human health.”7
Let’s raise a cheer for food safety and the little-known benefits of one of our favorite mints: Spearmint essential oil!
- Snoussi M, et al. Mentha spicata Essential Oil: Chemical Composition, Antioxidant and Antibacterial Activities against Planctonic and Biofilm Cultures of Vibrio spp. Strains. Molecules. 2015 Aug 7;20(8):14402-29.