Bacteria more effective than chemical repellents in controlling insects and diseases

A soil bacterium prevalent in the wild has proven to be as effective as an insect repellent as the most commonly used active chemical ingredients on the market.

Scientists expect microorganisms of the genus Xenorhabdus to be used as weapons in the fight against mosquitoes, such as as dengue, malaria and zika viruses, and other parasites. like ticks.

"We knew that Xenorhabdus bacteria killed insects and produced certain chemicals with antibiotic, antifungal and insecticidal properties," biologist Mayur Kumar Kajla, a researcher at the University of Wisconsin-Madison, told BBC News. in the USA. National Institute for Malaria Research, New Delhi, India.

"Incidentally, in the laboratory, we found, by examining several samples of isolated bacteria, that, mixed with blood, they prevented the mosquitoes from feeding, we then considered the possibility of producing a mosquito repellent."

that the idea is effective. Compounds obtained from Xenorhabdus repelled insects as effectively as commercial anti-DEET and anti-picaridine products.

The scientists involved in the research believe they have succeeded in opening up a new way of containing mosquitoes and other disease-carrying parasites – with one advantage: it would be a natural non-synthetic repellent, but also effective against bites.

The research was published Wednesday by the journal Science Advances. According to the publication, the discovery "may help reduce the risk of dangerous pathogens such as dengue, malaria and zika".

"Many types of bacteria are already used in pharmaceutical applications, such as antibiotics." Previous studies on bacteria of the genus Xenorhabdus had already shown several bioactivities such as antibiotic, antifungal and insecticidal properties in the secondary metabolites produced by the bacterium. This is the first time they have explored their ability to act as natural repellents against mosquitoes, "said the newspaper in a statement.

Essays

Kajla and his team used a feeding system cell to monitor bacterial compounds capable of acting on insects.In the laboratory, we used the species Xenorhabdus budapestensis of the bacterium.

The scientists then tested the action of the compounds obtained and compared with two synthetic repellents, one DEET compound and the other picaridine.The natural formula, obtained from the bacterium, was as effective, if not more, than the synthetic formula by repelling the Aedes aegypti – the mosquito that transmits dengue fever

They were also effective against two other mosquito vectors, Anopheles gambiae and Culex pipiens, and researchers' expectations and compounds could be used s a greater variety of other transmissible mosquito species.

Use in humans

"Up to now, we have described the repellent active compounds produced by these bacteria and have shown that these compounds are potent to repel Aedes mosquitoes, Anopheles and Culex in lab tests.The next steps are to evaluate their toxicity in cell cultures and animal models before they can be tested on human skin, "said Kajla.

The scientist explains that bacteria "produce these compounds in their growth medium", that is, a liquid diet in which researchers develop bacteria. This means that "repulsive active compounds can be isolated from bacterial cultures".

"Thus, the purified compounds are used in repellency tests, not the bacteria themselves," says the biologist.

"In this way, repellent active substances, not bacteria, can become the active ingredient of a repellent formula, very similar to DEET-based market repellents."

Synthetic products

The two synthetic products that have been compared to the compound extracted from bacteria are the active ingredients among the most common in repellents on sale today. DEET is a chemical compound commercially indicated in Brazil under the name of diethyltoluamide. Its official scientific name, according to the International Union of Pure and Applied Chemistry, is N, N-diethyl-3-methylbenzamide.

Protects against insects, ticks and other arthropods and is used to prevent diseases such as dengue, malaria, yellow fever, among others.

The compound was developed by the US military. It was first tested as a pesticide in rural areas and used as the first repellent only by the army since the Second World War. Its use for civilian purposes began in 1957.

Picaridin, also known as icaridine or KBR 3023, is an active substance derived from pepper. Its official scientific nomenclature is 2- (2-hydroxyethyl) -1-methylpropyl acid of 1-piperidinecarboxylic acid.

It is an effective product against mosquitoes transmitting dengue fever, yellow fever, leishmaniasis, in addition to the vector tick of spotted fever.

Historically, French infectious doctor Eric Lundwall told the army that he was used to missions in French Guiana – because of the high incidence of malaria in the Amazon region.

In 2002, picaridine was marketed. In Brazil, products containing this active ingredient arrived on tablets in 2005.

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