Quorum sensing inhibitors or how plants can fight bacterial infections

QUORUM SENSING EXPLAINED

Quorum sensing, also known as bacterial intracellular communication, is the mechanism by which cells are able to control basic cellular activities and coordinate their actions [1], and the way bacteria is able to infect our bodies in a coordinated and structured way. Quorum sensing is, in other words, the mechanism used by bacteria to synchronize their behaviour, including the virulence of their attacks, antibiotic resistance, biofilm formation (communities of microorganisms attached to a surface [10])...etc, and all this in order to react appropriately to external signal and manage their primary goal, a bacterial infection. Breaking bacterial intracellular communication is a way to stop bacterial infections on a natural way that scientists and pharmaceutical companies have investigated since recent years to fight multi-drug resistance of certain bacterias.

Where traditional antibiotics failed to treat infections caused by bacterial biofilms and multi-resistant bacteria as gram-negative bacteria, quorum sensing inhibitors managed to stop infection, something specially interesting in gram-negative bacteria, shielded in a protective film and immune to most known antibiotics and for which quorum sensing seems to be the last line of defense.

NATURAL ANTIBIOTICS WITH QUORUM SENSING PROPERTIES

Until now it was believed that marine algae active constituents

were the only natural source of anti-quorum sensing natural molecules and phytochemicals, however it seems scientist and laboratories have found other sources or quorum sensing inhibitors, guess what? Once again herbs, source of natural antibiotic compounds known as quorum sensing inhibitors.

Emulating Sean Connery and Lorraine Bracco in Medicine Man, scientists, biologists and biochemists from multiple companies are on the search for new antibiotics that will fight multi-drug resistance of certain bacterias. One of this companies is Quorumex, a company that as his President and CEO Dr. John McAfee, founder of McAfee Anti-virus and Tribal Voice said, has as a philosophy "to re-invent the way modern medicine combats and disarms pathogenic bacteria". With this purpose Quorumex has scientist and biochemists investigating rain forest herbs and their active constituents on the search for plants that will exert this anti-quorum sensing properties.

In 2011 Quorumex released Qto-QX, a medicine based on quorum sensing disruption that was able to fight common ear infections. Others as Ulcer-QX and Oral-QX and anti-Helicobacter pylori bacteria drug and a mouthwash based on the same anti-quorum sensing principle.

Scientists, biologists and biochemists from multiple companies are on the search for new natural antibiotics.

OTHER NATURAL ANTIBIOTICS OR NATURAL QUORUM INHIBITORS

Horseradish (Armoracia rusticana, Cochlearia armoracia), a plant rich in isothiocyanate, which is an active constituent of other members of the Brassicaceae family, exerted a powerful anti-bacterial property against the Pseudomonas aeruginosa pathogen [2], a property that was already know on another natural antibiotic as garlic (Allium sativum), in spite the results against that pathogen using garlic were considerable lower [3], however garlic extract did show certain antibiotic properties against Pseudomonas aeruginosa [5,6]. 

Another natural quorum sensing inhibitor is vanilla extract (Vanilla planifolia), a natural antibiotic that can inhibit bacterial quorum sensing and prevent bacterial pathogenesis on at least Chromobacterium violaceum CV026.

CALLISTEMON VIMINALIS QUORUM SENSING INHIBITORY PROPERTIES

Callistemon viminalis antibacterial properties are probably exerted by this plant due to its quorum sensing inhibitory properties. Quorum sensing, also known as bacterial intracellular communication, is the mechanism by which cells are able to control basic cellular activities and coordinate their actions, and the way bacteria is able to infect our bodies in a coordinated and structured way. Breaking bacterial intracellular communication or quorum sensing, is a way to stop bacterial infections on a natural way that scientists and pharmaceutical companies have investigated since recent years to fight multi-drug resistance of certain groups of bacteria.

Callistemon viminalis, together with Conocarpus erectus (Combretaceae), Chamaecyce hypericifolia (Euphorbiaceae), G. Don (Myrtaceae), Bucida burceras (Combretaceae), Tetrazygia bicolor (Melastomataceae), and Quercus virginiana (Fagaceae), showed quorum sensing inhibitory properties agains Chromobacterium violaceum and Agrobacterium tumefaciens bacterial strains [9].

REFERENCES

[1] Wikipedia (http://en.wikipedia.org/wiki/Cell_signaling)

[2] Food as a source for QS inhibitors: Iberin from Horseradish Revealed as a Quorum Sensing Inhibitor of Pseudomonas aeruginosa. Jakobsen TH, Bragason SK, Phipps RK, Christensen LD, van Gennip M, Alhede M, Skindersoe M, Larsen TO, Høiby N, Bjarnsholt T, Givskov M. Department of International Health, Immunology and Microbiology, University of Copenhagen, DK-2200 Copenhagen, Denmark.

[3] Garlic as an inhibitor of Pseudomonas aeruginosa quorum sensing in cystic fibrosis--a pilot randomized controlled trial. Smyth AR, Cifelli PM, Ortori CA, Righetti K, Lewis S, Erskine P, Holland ED, GivskovM, Williams P, Cámara M, Barrett DA, Knox A. Division of Child Health, University of Nottingham, Nottingham, UK.

[4] Quorum-sensing signals in the microbial community of the cabbage white butterfly larval midgut. Borlee BR, Geske GD, Robinson CJ, Blackwell HE, Handelsman J. Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706, USA.

[5] Inhibition of bacterial quorum sensing by vanilla extract. Choo JH, Rukayadi Y, Hwang JK. Department of Biotechnology, Yonsei University, Seoul, Republic of Korea.

[6] Screening for quorum-sensing inhibitors (QSI) by use of a novel genetic system, the QSI selector. Rasmussen TB, Bjarnsholt T, Skindersoe ME, Hentzer M, Kristoffersen P, Köte M, Nielsen J, Eberl L, Givskov M. Center for Biomedical Microbiology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.

[7] Rational design and synthesis of new quorum-sensing inhibitors derived from acylated homoserine lactones and natural products from garlic. Persson T, Hansen TH, Rasmussen TB, Skindersø ME, Givskov M, Nielsen J. Department of Natural Sciences, Bioorganic Chemistry Section, Royal Veterinary and Agricultural University, Frederiksberg C, DK-1871, Denmark.

[8] An inhibitor of bacterial quorum sensing reduces mortalities caused by Vibriosis in rainbow trout (Oncorhynchus mykiss, Walbaum). Rasch M, Buch C, Austin B, Slierendrecht WJ, Ekmann KS, Larsen JL, Johansen C, Riedel K, Eberl L, Givskov M, Gram L. Danish Institute for Fisheries Research, Department of Seafood Research, Søltofts Plads, c/o Technical University of Denmark, Lyngby, Denmark.

[9] Anti-quorum sensing activity of medicinal plants in southern Florida.
Adonizio AL, Downum K, Bennett BC, Mathee K.
Department of Biological Sciences, Center for Ethnobiology and Natural Products, CENaP, Florida International University, 11200 SW 8th Street, University Park, Miami, 33199, USA.

[10] Biofilm formation as microbial development.
O'Toole G, Kaplan HB, Kolter R.
Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.