Ants show new promise as a source of powerful antibiotics

Has a crucial component to the development of human medicine been hiding under our feet?

Auburn University Assistant Professor of Entomology Clint Penick and a team of graduate students may have found that ants are far ahead of humans in antibiotic innovation. "In our study, we tested how ants use antibiotic compounds to fight off pathogens and asked why their chemical defenses remain effective over evolutionary time," Penick said. 

"Humans have relied on antibiotics for less than a century, yet many pathogens have already evolved resistance, giving rise to 'superbugs.'' Ants, by contrast, have been using antibiotics for tens of millions of years, and they might hold the key to using these powerful drugs more wisely.

The team looked at just six ant species, all found easily in the Southeastern United States.

These are the ants that live in our backyards and live on college campuses. And yet some of the most powerful antibiotics we found come from ants we typically consider pests, like fire ants."

Clint Penick, Assistant Professor of Entomology, Auburn University  

In a study recently published in the Biological Journal of the Linnean Society, the team tested two hypotheses about how ants might be using antibiotics without promoting antibiotic resistance. First, they examined whether ants might produce multiple types of antibiotics using different chemical compounds. 

"It's just like when you go to the doctor, and they try one antibiotic. If it's not working, they're going to try another one," Penick said.

When the team tested whether extracts using different solvents showed antimicrobial activity, they found evidence that ants do indeed produce multiple classes of antimicrobials. "Just like us, ants seem to have different medicines in their medicine cabinet that they can try if the first one doesn't work."

The second hypothesis they tested was whether ants produce compounds targeted to specific microbes - one of science's biggest challenges today.

"If we just dump antibiotics into systems to kill everything, we're not only killing our target pathogen but also killing all these other microbes that aren't harming us," Penick explained. "By doing that, we're helping breed resistant genes in non-target populations that can lead to drug resistance down the line."

The team found evidence that ants produce compounds specific to different pathogens: some that target fungi, others that target gram-negative bacteria, and still others that act on gram-positive bacteria.

"This is something that people are really interested in within human medicine - figuring out more targeted antibiotics," Penick said. "And it looks like ants have been doing this for millions of years."

While not the primary focus of the paper, the team found that nearly all of the ant species tested killed an emerging human superbug - Candida auris. This pathogen has been spreading in hospitals with few options for control, yet ant extracts were highly effective against it.

The work was funded by the Alabama Agricultural Experiment Station, and the team included Katy Chon, Kennesaw State University graduate student, and Darmon Kahvazadeh, Auburn entomology and plant pathology graduate research assistant. 

The next step, said Penick, is to look at what types of compounds ants are producing and how they're using them.

"It could help inform our own practices or potentially we could discover new compounds that have medical importance," Penick said. "Our findings suggest that ants could represent a vast and largely untapped source of new antibiotics, including ones capable of combating today's most dangerous drug-resistant infections."