Ants might be carrying the medicines of the future, according to an analysis of antibiotics the insects are naturally producing.

A study in the journal Royal Society Open Science suggests that many ant species have antimicrobial substances on their exoskeletons, including ants that have not been previously studied for their bacteria-fighting skills. The finding comes from an investigation into the ants’ power, in which scientists measured how much bacteria grew in the presence of the exoskeleton substances, as compared to the bacterial growth in their absence.

The researchers tested the antimicrobial properties of 20 diverse ant species.

They did not see any effect in about 40 percent of the species, the study said, highlighting the need for additional research into which ants are worth pursuing for their medicinal value.

“One species we looked at, the thief ant (Solenopsis molesta), had the most powerful antibiotic effect of any species we tested — and until now, no one had even shown that they made use of antimicrobials,” study co-author Adrian Smith said in a statement from North Carolina State University. “Finding a species that carries a powerful antimicrobial agent is good news for those interested in finding new antibiotic agents that can help humans.”

According to the study, the test on the thief ant showed that its antimicrobial power prevented any bacteria from growing at all.

The researchers also reported that the discovery of so many ant species whose exoskeleton substances don’t fight off microbes contradicts previous ideas that all ants have some sort of antibiotic agent on their bodies.

“We thought every ant species would produce at least some type of antimicrobial,” lead study author Clint Penick said in the statement. “Instead, it seems like many species have found alternative ways to prevent infection that do not rely on antimicrobial chemicals.”

The team is now looking to better understand what different kinds of bacteria the different ants can fight off and what those alternative antimicrobial defenses may be.

“In light of the rise in antibiotic resistant pathogens that infect an estimated 2 million people in the United States each year, research on pathogen control in social insects could provide future insights for dealing with antibiotic resistance,” the study said.