An antiseptic used in WWI hospitals has been revived after seven decades, and is showing great promise in preventing the common cold, and could be the key to fighting antibiotic resistance - one of the biggest ever threats to global health.

The simple antiseptic, made from coal tar, was replaced by penicillin after the war, and fights both viral and bacterial infections in an entirely different way - one that could prevent pathogens from mutating to outsmart our medications.

"It was replaced … by penicillin, but we think that with new bacteria [that are] more and more resistant to treatment, it may do a comeback," one of the researchers behind the discovery, Michael Gantier from the Hudson Institute of Medical Research in Australia, told ABC News.

"It's very cheap to make, it's not something you would make if you were a private company trying to make money on drugs."

Called Acriflavine, the antiseptic is derived from coal tar, and comes in the form of a reddish brown or orange powder.

It was first used in the early 1900s as a topical treatment to prevent flesh wounds from getting infected, and was widely used in hospitals and homes to treat everything from urinary tract infections and gonorrhoea until the 1940s, when penicillin came to the fore.

It's now been more than 70 years since penicillin became the most important tool we have to fight bacterial infections, and its days appear to be numbered. 

Many of the deadliest pathogens in the world have managed to mutate into forms that our penicillin-based drugs can't recognise or destroy, and now antibiotic-resistant bacteria kill roughly 700,000 people each year around the world.

In addition to common hospital superbug, methicillin-resistant Staphylococcus aureus (MRSA), experts are now concerned that gonorrhoea is about to become resistant to all remaining drugs, and there are already resistant strains of tuberculosis, pneumonia, and E. coli being circulated.

If we don't find a viable replacement for penicillin soon, antibiotic-resistant bugs are predicted to kill 10 million people every year by 2050.

So what makes Acriflavine a better fit than penicillin for our very serious superbug problem?

Gantier and his team revisited the drug that showed so much success in the early 20th century, because until now, no one had investigated how it actually works.

"Early scientific literature notes its antibacterial qualities in test tubes, but its very effective action on the skin has never been fully defined," Gantier told Bill Condie at Cosmos.

The team investigated its behaviour in human cell cultures, and figured out that it binds to the DNA of the patient to kick the immune system into action when a viral infection was taking place.

At the same time, the antiseptic also binds to viral DNA in the body, slowing the spread of viruses as the immune system prepares itself.

"We have shown for the first time that Acriflavine binding to cellular DNA could activate the host immune system, unleashing a powerful immune response on a potentially broad range of bacteria," Gantier said.

When the team investigated the drug's effect on a common cold virus in human lung tissue, they found that cells that had been treated with Acriflavine three days prior to the infection had a faster immune response to the virus, and the virus spread more slowly through them than in the control cells.

"In a patient, that would mean that if you were to encounter the virus, you wouldn't feel as sick and you would clear the infection quicker," Gantier told The Sydney Morning Herald.

The results suggest that the drug could be inhaled in small doses as a preventative treatment for patients who are at a high risk of being infected by specific viral infections, or populations threatened with viral outbreaks.

While the researchers have so far only tested Acriflavine's response to viral infections, Gantier says the way it works will likely apply to bacterial infections too - even antibiotic-resistant ones, because it behaves nothing like penicillin.

"Our study indicates that Acriflavine stimulates the host immune system, rather than simply killing bacteria, suggesting it wouldn't be as likely to drive mutations in bacteria - showing a safeguard against resistance and a potential alternative to current antibacterial drugs," he told Cosmos.

The team has yet to conduct clinical trials to test the antiseptic's effectiveness against current strains of viral and bacterial infections, but they're hoping the promising results from lab experiments, and the fact that the drug is currently used by developing nations because of how cheap it is, means they shouldn't have any problems getting approval to observe its effects in actual patients.

Let's hope it continues to show this much promise in future experiments, because we need an answer to antibiotic resistance now, and it would be pretty damn cool if the drug that penicillin replaced becomes the drug that replaces penicillin.

The study has been published in Nucleic Acids Research.