Antibiotic Herbs Interfere with Bacteria Quorum Sensing

The ability of antibiotic herbal medicines to inhibit bacterial infections without producing antibiotic resistance may now be better explained. Turns out these antibiotic herbs block the ability of microbes to utilize their quorum sensing capacities.

We’ve previously reported on the worldwide epidemic of antibiotic-resistant superbugs.

We’ve also reported research confirming that many herbs possess significant antibiotic and antifungal potency. We’ve also shown scientific studies proving that some herbs have more antibiotic potential than many of our pharmaceutical antibiotics.

We have also shown research finding that some of these antibiotic herbs do not allow bacteria to become resistant like pharmaceutical antibiotics do. Research may have landed on one of the reasons for this: Antibiotic medicinal herbs counteract infective bacteria’s quorum sensing abilities. Read on to better understand how this works.

Why medicinal herbs don’t become antibiotic resistant

Why don’t bacteria develop resistance to many antibiotic herbs as they do against pharmaceutical antibiotics? This issue often presents more than a curiosity for many scientists.

We have responded that one of the factors relates to the reality that plants are living organisms just as bacteria are. Because plants are alive, they are constantly developing new combinations of phytochemicals that inhibit the growth of bacteria.

And we do find that over time, plants evolve in their production of biochemicals, depending on their environment. For example, we find that plants that grow in a particular location will produce a unique combination of biochemicals that happen to inhibit the microorganisms that surround it in this location.

But this alone doesn’t provide the entire answer for why those microbes don’t develop a resistance to whatever biochemical combinations the plant may produce.

Enter the prospect of herbs’ interfering with microbes’ quorum sensing abilities.

What is quorum sensing?

Quorum sensing is the method that microorganisms use to communicate. Microorganisms utilize quorum sensing to communicate with each other and the colony as a whole. Communications range from external environmental factors, threats, and survival to other factors regarding sustaining the life of the colony.

We might compare quorum sensing to how humans communicate with each other with regard to potential enemies, where to find the best foods and how to cure diseases.

Today, in addition to verbal communication, humans use the television or the internet to communicate with each other. This allows us to exchange ideas that affect our survival and life-sustaining factors. These also include communications relating to common threats and even facilities for mating.

In other words, human communications help our societies (cultures) grow and prosper.

Quorum sensing is what bacteria do to serve the same purposes. The communication system of quorum sensing is most known to exist between individual microorganisms and the larger colony of microbes that surround it. A colony that grows will typically grow as a result of positive quorum sensing. The microbes will be communicating with the rest of the colony regarding their ability to eat and grow in the current environment.

Quorum sensing is also considered biocommunication because it utilizes a combination of electromagnetic radiation and biochemistry. This is for the most part invisible, although sometimes quorum sensing will yield effects that we can see.

Bioluminescence is a result of quorum sensing

For example, when we see bioluminescence on the surface of the ocean or other waterways at night – this is produced by quorum sensing. In this case, the algae microorganisms are communicating with each other, and this particular quorum sensing communication happens to also yield beautiful colors on the surface of the water.

Bioluminescence allowed scientists to discover microbe quorum sensing. The strange lights seen at night on the water were investigated for decades. Eventually, researchers finally concluded that the algae were communicating with each other.

Since these discoveries, scientists have now established that just about every microbe utilizes quorum sensing.

Herbs that interfere with quorum sensing

Scientists leading the way in this research on medicinal herbs have come from the universities of India. India provides more research funding for medicinal herbs. Because of this, many recent discoveries regarding herbal medicine’s ability to treat disease and fight infection have come from India’s hospitals, medical schools, and research laboratories.

For example, in a 2017 study, scientists from India’s Yenepoya Research Center at Yenepoya University researched the medicinal herb Cassia alata L. Cassia alata L. is also called wild Senna herb and has been named Senna alata L. by the USDA.

Senna is known not only for its laxative effects but its ability to fight off gut bacterial infections.

The researchers produced extracts from the leaves of the plant. They also separated certain metabolites during the extraction process. These metabolites were constituents of the Senna herb.

The researchers proceeded to test the extracts of Senna against different strains of the bacteria species Chromobacterium violaceum. This particular bacteria species can infect the gut and will produce a violet (violacein) color as a result of their quorum sensing. This allowed the scientists to test the ability of the Senna extracts to affect the quorum sensing of the different C. violaceum species.

The researchers found the Senna extracts did interfere with the quorum sensing of the C. violaceum bacteria. This helped to prevent the C. violaceum bacteria colonies from growing.

The bacteria species’ ability to colonize and form biofilms was virtually blocked by the interference in the Senna extracts to their quorum sensing abilities.

In other words, it was a central reason why Senna provides an antibiotic effect.

The researchers then tested the Senna extracts against another disease-causing bacteria, Pseudomonas aeruginosa. This bacteria will grow around wet, humid areas and will infect the skin, oral cavity, and gut. This species will often colonize around the edges of hot tubs and baths.

The bacteria also presents a good example for measuring quorum sensing as it produces a reddish agent called pyocyanin as a byproduct of its quorum sensing communications.

The researchers also found that the Senna extracts inhibited the growth of the P. aeruginosa bacteria. And just as they had done with the other bacteria, the Senna blocked the quorum sensing abilities of the P. aeruginosa bacteria.

Moreover, the researchers found that some constituents of the Senna plant also inhibited the quorum sensing. Several of these individual constituents produced quorum sensing blocking. The most notable constituents were quercetin, quercetrin and kaempferol.

These also happen to be constituents found in garlic, onions, and other antibiotic plants.

The researchers concluded:

“Present study demonstrates the quorum sensing inhibitory activity of metabolites from Cassia alata, an important medicinal herb which is commonly used worldwide in the treatment of infections caused by microorganisms. An extract prepared from the leaves of the plant showed activity against quorum sensing in Chromobacterium violaceum and was also effective against attenuating the quorum sensing controlled virulence factors in Pseudomonas aeruginosa.”

Other herbs inhibit quorum sensing

In 2016, Indian researchers tested an extract of Gotu kola (Centella asiatica) using the Chromobacterium violaceum bacterium. The researchers found the Gotu kola extracts also blocked the quorum sensing ability of the bacteria, as well as blocking the infective potential (biofilm creation) of the bacteria. It also interfered with the bacteria’s proteolytic and elastolytic activities – their ability to break down proteins and proteins of elastic tissue, respectively.

In another 2017 study, researchers from India’s University of North Bengal tested the quorum sensing blocking ability of 61 medicinal herbs. The researchers also utilized the same two bacteria, Chromobacterium violaceum (violacein) and Pseudomonas aeruginosa (pyocyanin).

While a number of herbs interfered with both quorum sensing and inhibited the bacteria, the researchers found that three plants blocked quorum sensing of the bacteria without affecting their growth. These three plant medicines were Fragaria nubicola (Himilayan flowers), Astilbe rivularis (Astilbe) and Osbeckia nepalensis (Nepal Osbeckia).

The interesting thing here is that by interfering with their quorum sensing, the plants can interfere with a bacteria colony’s ability to infect the body without necessarily killing off the bacteria.

Ameliorating infection without killing

The mass killing of bacteria only raises their hackles. This would occur with any species. Imagine if an alien race began killing off large populations of humans with bombs. We would immediately come together to figure out how to fight off the invading force.

This would create an effective ‘war of the worlds’ so to speak.

This is what is going on with our fight with infective bacteria. In this ‘war of the worlds’ between humans and bacteria, we are trying to kill them off with our antibiotic ‘bombs.’ They, in turn, are fighting us by figuring out how to get around these antibiotics.

A better way is to use what nature has been utilizing for millions of years. That is, to simply prevent bacteria from invading our bodies by consuming medicinal plants when needed. This effectively blocks the ability of the bacteria to communicate – preventing colonies from building up in our bodies.

Such a strategy, in turn, allows our immune system and probiotic colonies to control any remaining (undoubtedly confused) bacteria. This control may take place in the form of colonies of competitive bacteria killing each other, or the immune system’s ability to kill off infections.

Interrupting the quorum sensing of bacteria also explains how plants can help prevent infections without the bacteria becoming resistant to the plant. That’s because the plant is blocking their communications rather than just going in and killing them off. That effectively drives them away and keeps them at bay.

Scientists from Belgium’s Free University of Brussels (yes, University should be free) have taken notice of this research. After reviewing the research, the researchers reported:

“Emergence and worldwide spreading of resistant bacteria to antibiotic have raised the importance for finding therapeutic alternative to compensate antibiotic drawbacks.”

Noting this urgent issue, the scientists continued,

“… targeting quorum sensing seems to be relevant to the struggle against bacterial infection.”

REFERENCES:

Rekha PD, Vasavi HS, Vipin C, Saptami K, Arun AB. A medicinal herb Cassia alata attenuates quorum sensing in Chromobacterium violaceum and Pseudomonas aeruginosa. Lett Appl Microbiol. 2017 Mar;64(3):231-238. doi: 10.1111/lam.12710.

Rasamiravaka T, El Jaziri M. Quorum-Sensing Mechanisms and Bacterial Response to Antibiotics in P. aeruginosa. Curr Microbiol. 2016 Nov;73(5):747-53. doi: 10.1007/s00284-016-1101-1.

Tiwary BK, Ghosh R, Moktan S, Ranjan VK, Dey P, Choudhury D, Dutta S, Deb D, Das AP, Chakraborty R. Prospective bacterial quorum sensing inhibitors from Indian medicinal plant extracts. Lett Appl Microbiol. 2017 Jul;65(1):2-10. doi: 10.1111/lam.12748.

Vasavi HS, Arun AB, Rekha PD. Anti-quorum sensing activity of flavonoid-rich fraction from Centella asiatica L. against Pseudomonas aeruginosa PAO1. J Microbiol Immunol Infect. 2016 Feb;49(1):8-15. doi: 10.1016/j.jmii.2014.03.012.

Vasavi HS, Arun AB, Rekha PD. Anti-quorum sensing activity of Psidium guajava L. flavonoids against Chromobacterium violaceum and Pseudomonas aeruginosa PAO1. Microbiol Immunol. 2014 May;58(5):286-93. doi: 10.1111/1348-0421.12150.