Aussies believe crocodiles key to fight against emerging disease threat

Because they have evolved to live in swamps, crocodiles are able to fight off infections that would harm humans.

Crocodiles are often associated with danger, but a new Australian study suggests these ancient reptiles will soon be saving lives.

Researchers discovered crocodile immune systems could be used as a template to help fight fungal strains which are becoming resistant to treatment.

La Trobe University researcher Scott Williams and his team decided to focus on saltwater crocodiles because the species has adapted to thrive in filthy microbe-rich environments. “They live in swamps, they’re always in fights and yet they rarely develop infection,” he told Yahoo News Australia.

Left - a crocodile in a green coloured tank. Right - Inside a hospital room with PPE to prevent the spread of disease.
Crocodile proteins could be used to help treat fungal infections in humans. Source: Getty (File)

Inside hospitals, resistance in fungi like Candida albicans is becoming a huge problem, particularly for the immunocompromised. "Any anytime you have a cannula or something where you're opening up the body, there's the potential that the fungus can get inside and then start to colonise and create disease in humans," Mr Williams said.

He believes if the discovery was pursued therapeutically, new treatments could be benefiting humans by 2033. “If you had a systemic infection, like some sort of sepsis, you could definitely give it intravenously, but also there’s been some work into developing these proteins into topical agents.”

How do crocodile proteins benefit humans?

The crocodile breakthrough, published in Nature Communications centres around defensin proteins that plants and animals use to fight microbial pathogens like bacteria, fungi and viruses.

Because humans and crocodiles have similar defensins, scientists are confident they can adapt them to serve both species.

What’s special about crocodile defensins is that they can turn themselves on and off depending on the pH levels, a mechanism that hasn’t been seen in any other plant or animal. “When it gets to the site of infection when the pH is lower and it's more acidic, it activates, and it can clearly infection,” Mr Williams said.

The molecule binds to the lipid membrane — the outside of the fungal cell — destabilising it by causing holes. Once the cell is ruptured its contents leak out and it dies.

Images provided to Yahoo News Australia show Candida albicans fungi turning orange as it dies after being targeted by the green-coloured defensins.

Left - Healthy fungal cells. Right - The outer membrane has turned green in parts. Small spots of orange in the same cells indicates they are dying.
Fungal cells (Candida albicans) before and after treatment. The green signal is the defensin and the orange shows that the cell is dead. Source: Nature Communications

Why could fungi be the next pandemic?

While the public is largely aware of problems associated with resistant bacteria, the threat posed by fungi has largely flown under the radar.

Most fungi prefer temperatures of around 30 degrees, so a key point that has prevented them from colonising humans is their high body temperature of around 37 degrees.

But as climate change increases temperatures across the globe, fungi is becoming more resistant to temperature. “The more accustomed they get to the rising climate, the more likely it is they’ll be able to then cross over and start to colonise humans,” Mr Williams warns.

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