Skin Microbiome Could Be Tweaked To Become Mosquito Repellent, New Study Suggests

A new study hints that tweaking skin microbes could serve as an effective way to stop mosquitoes from biting and, consequently, curb mosquito-borne diseases from spreading.

Attracting Mosquitoes

Mosquitoes have been known to sniff out humans to bite. They do so by zeroing into the unique scents of people, which include the chemicals that the skin's sweat and oil glands release.

Different molecules are also released by the sweat glands. These molecules are then broken down by skin microbes so that they may use the molecules as nutrients. The nutrients' metabolism releases tiny molecules that have unique scents, which may attract mosquitoes.

Mosquito Repellent

A new study entitled "Identification of human skin microbiome odorants that manipulate mosquito landing behavior" was able to identify that the chemicals that the skin microbiome generates actually have the capacity to repel microbes. This could particularly shoo away a mosquito species known as Aedes aegypti, which spreads illnesses like dengue, Zika, yellow fever, and chikungunya.

The findings suggest that tweaking the skin microbiome to release specific scents could be effective in preventing mosquitoes from biting. According to researchers, such an approach could be theoretically safer compared to using synthetic mosquito repellents that may lead to skin irritation and that could wear off in a matter of hours.

According to Illiano Vieira Coutinho-Abreu, the study's first author and a researcher from the University of California, San Diego, the scientists were motivated to discover new tools to prevent mosquito-borne illnesses from spreading. He explains that new tools are necessary due to how populations of mosquitoes are becoming resistant to insecticides. The parasites carried by the pests are also fostering drug resistance.

The team then decided to look into the skin microbiome of humans. Coutinho-Abreu explains that aiming for the sources of cues that attract mosquitoes may result in protection against bites and prevention of transmission.

The researchers nurtured several bacterial strains from the Corynebacterium and Staphylococcus genera. These are two broad microbial groups that can be found on the human skin. The bacteria were grown in conditions that mimic those found on the skin. The researchers then profiled the volatiles, which are typically smelly chemicals that quickly evaporate, that the microbes released. Some volatile effects were tested on the behavior of the mosquitoes.

The team put up a buzzing pest chamber for them to do this. One of the chamber's ends had a plastic mesh covered with the volatile compound, while the other end had a plastic mesh with an odorless compound. They then gauged the time that the mosquitoes spent nearing the skin volatile compared to the compound that was odorless.

Three skin volatiles were observed to repel mosquitoes. These were geraniol, 3-methyl butyric acid, and 2-methyl butyric acid. The first one is a crucial component of rose oils and citronella, while the last two can be commonly found in fruits, such as apples.

Findings also confirmed that the pests were attracted to bacteria-produced lactic acid, which is known to attract mosquitoes. Interestingly, there were some skin volatiles that only drew in mosquitoes when they were mixed with lactic acid. Such observations suggest that lactic acid may affect how other skin chemicals could attract these pests.

Based on such findings, the researchers propose changing the skin microbiota to stop the production of chemicals that attract and to produce chemicals that repel. The researchers also suggest that tweaking the skin microbiome to reduce lactic acid production could prevent mosquitoes from biting and, consequently, prevent mosquito-borne illnesses from spreading.

Further Study

Since the release of this study, the researchers have also released new results that support the findings. However, their new results are yet to be peer reviewed.

As part of this new study, the researchers knocked a gene from the synthesis pathway of lactic acid in two resident bacteria of the human skin. This was done to prove the key role of lactic acid in attracting mosquitoes. The application of genetically engineered bacteria to lab mouse skin significantly decreased the number of mosquitoes that landed on the mice for several days. Such findings show that mosquitoes may be less likely to feed on humans covered with such skin bacteria knockout lines.

Moving forward, steps to be taken may include testing the safety of such applications and seeing if other mosquito species could also be repelled. Eventually, the team may also see human clinical trials of such a treatment.