Bacteria more effective than chemical repellents in controlling insects and diseases | Science and health

Microorganisms of the genus Xenorhabdus are expected to be used as weapons to control mosquitoes, such as dengue fever, zika transmitters, and other pests. , such as ticks.

"We knew that Xenorhabdus a bacterium killed insects and produced certain chemicals with antibiotic, antifungal and insecticidal properties," biologist Mayur Kumar Kajla, a researcher at the University of Wisconsin. Madison, United States and the National Institute for Malaria Research in 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 had then glimpsed the possibility of producing an anti-mosquito."

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 various 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, "the paper said in a statement.

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

The scientists then tested the action of the compounds obtained and compared with two synthetic repellents, one DEET compound and the other from picaridine.The natural formula, obtained from the bacterium, was as effective or more effective than the synthetic formula by repelling the Aedes aegypti – the mosquito that transmits dengue

They were also effective against two other vector mosquitoes, the Anopheles gambiae and Culex pipiens . Researchers' compounds could be used in a wider variety of other transmissible mosquito species.

"Up to now, we have described the repellent-active compounds produced by these bacteria and have shown that these compounds are potent in repelling Aedes, Anopheles and Culex mosquitoes during laboratory tests. Steps are to evaluate their toxicity in cell cultures and in animal models, before they can be tested on human skin, "says Kajla.

The scientist explains that bacteria "produce these compounds in their growth medium", that is to say 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, the repellent active substances, and not the bacteria, can become the active ingredient of a repellent formula, very similar to DEET-based market repellents."

The two synthetic products compared to The compounds extracted from bacteria are the active ingredients among the most common repellents currently on the market. 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 fever, 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 vectors of dengue fever, yellow fever, leishmaniasis, in addition to the vector tick of spotted fever.

Historically, French infectious doctor Eric Lundwall told the army to take part in missions in French Guiana, because of the high incidence of malaria in the Amazon region.