Courtesy of Alexander Wild / University of Wisconsin
Nobody likes a cockroach in their house. But before you smash the unwelcome intruder, consider the following: This six-legged animal could someday save your life.
Right. Insects known to spread disease may help to heal them. Or rather, the microbes living in them could. Scientists have discovered dozens of microorganisms that live in or on insects that produce antimicrobial compounds, some of which may hold the key to developing new antibiotics.
You can not come too soon. There are more and more infections resistant to conventional antibiotics and the pipeline of new antibiotics has slowed down to a trickle.
"There is a growing demand [for antibiotics]and a smaller supply, "explains Gerry Wright, who heads the Michael G. DeGroote Institute for Infection Research at McMaster University.
Most antibiotics have been detected by soil-borne bacteria. However, Cameron Currie, professor of bacteriology at the University of Wisconsin-Madison, says the search for new antibiotics has become increasingly futile.
"They always find familiar antibiotics," says Currie. "There is a general feeling that the well of antibiotics is dry from the soil."
Fortunately, there is another well. Currie and a team of 28 researchers have recently published a work in Nature Communications It turns out that some of the bacteria living in insects can really kill the germs that make people sick.
"There are an estimated 10 million species [of insect] On the planet, "says Currie. This implies a huge potential for a lot of new things [antibiotic] Links. "
Each insect contains a whole ecosystem of microorganisms, just like the microbiome found in humans. There is one property that many of these insect-related microbes share, says Jonathan Klassen, Assistant Professor of Molecular and Cell Biology at the University of Connecticut and author of the study.
They do not get along well.
And if you do not get along with each other, it means they are constantly trying to kill themselves by biochemical warfare. Many of the microorganisms in insects make compounds that are toxic to other microbes – essentially natural antibiotics.
Some of these natural antibiotics caught Currie's attention during his studies as they studied leafcutter ants.
Leafcutter ants are among the most productive gardeners of nature. They do not actually eat the cut leaves – instead, they breed a special kind of mushroom for food. Still, being a mushroom farmer is not easy.
"Like human agriculture, ants have problems with disease," says Currie. "I found a specialized pathogen attacking its mushroom garden."
Fortunately, the ants have a tool to deal with the problem. A bacterium that lives on the exoskeletons of the ants produces a toxin that kills the pathogen. Like the pesticides that a gardener uses, the toxin keeps the garden of the ants disease-free.
The discovery inspired Currie's curiosity. If ants could use these bacterial compounds to treat diseases in their fungal gardens, could doctors use them to treat human diseases? If so, what other insects could carry microbes that fight disease?
To answer these questions, Currie and his team spent years collecting thousands of insects, including cockroaches, from Alaska to Brazil.
"Every few months, someone would go somewhere to collect something," recalls Klassen, who was a postdoctoral researcher at the time.
The team tested bacteria from each insect to determine if they could kill common human pathogens E coli and methicillin resistant Staphylococcus aureus (MRSA). They then compared the results of insect strains with strains grown from plants and soil.
"That really surprised us [insect strains] were not only so good, but seemed to be better off [pathogens]"Says Currie.
Test a new antibiotic
After a scientist has discovered that a bacterial strain can kill germs, the next step in drug development is to determine which bacterial compound is responsible for the antimicrobial activity – like a cook looking for the secret ingredient in a particularly delicious soup ,
Currie's team had found dozens of promising bacterial strains in insects. And everyone could make a secret ingredient that could be a new antibiotic compound.
That was a big achievement. However, the researchers went a step further. They isolated a compound from a particularly promising bacterial strain and showed that it can inhibit fungal infections in mice, an important step in drug development.
The compound, cyphomycin, is found in Brazilian mushroom ants, close relatives of the ants that Currie studied as a graduate student. Although it is by no means an approved drug, research shows that antibiotics that are new in science can be isolated from insects.
Wright, an antibiotic researcher who did not participate in the study, says earlier research has shown that some species of insects contained antimicrobial compounds. However, this is the first study to fully demonstrate that insects as a group are a promising source of new antimicrobials.
"No one on this scale has ever done anything," says Wright.
Currie hopes that someday Cyphomycin will be approved for the treatment of fungal infections in humans. Before this happens, it has to be tested for years.
"It [cyphomycin] is a million miles away [from approval]"Says Wright." That's the reality of drug discovery. "
However, researchers have already overcome one of the toughest hurdles in drug development, demonstrating that the compound works in mice, Wright said.
For classes, the stakes are too high, so as not to try.
"Efforts like this study are critical to keeping the antibiotic pipeline running so the disease does not gain the upper hand," he says.
In the end, the consequences of a world without antibiotics are enough to get scientists looking for new medicines in unconventional places – even if it means looking for a cockroach.
Paul Chisholm is a freelance science journalist in Rapid City, S.D. You can reach him on Twitter: @ PaulJChisholm,