Chemical moves from herbicide to hospital

A compound found in common herbicides may hold the key to saving millions of lives.

International researchers say chlorimurion ethyl is showing early potential to fight hospital-acquired human fungal pathogenic infections by inhibiting a key enzyme produced by two species, Candida albicans – a common intestinal yeast linked to severe illness – and Cryptococcus neoformans, another yeast that can cause a disease called cryptococcosis, especially in people with compromised immune systems.

“In studies in the petri dish and with mice it was highly effective at preventing proliferation of growth,” says Luke Guddat from the University of Queensland (UQ) in Australia, which led the project.

“By inhibiting this enzyme you’re removing a key metabolic step that makes three types of amino acids, which these infections need to grow.

“And most importantly, humans don’t have this enzyme –  we obtain these amino acids from our food – so there’s very little chance that these compounds will be toxic to humans, a factor which limits the use of many of the other currently prescribed antifungal drugs.”

In their study, published in the journal Proceedings of the National Academy of Sciences, the researchers tested five families of compounds to see if they could inhibit the enzyme, known as acetohydroxyacid synthase (AHAS). Chlorimurion ethyl was the stand-out candidate.

“We thought this was a good idea, since plants and fungi have a similar enzyme that these chemicals inhibit, and it turns out we were correct,” says UQ’s Mario D. Garcia.

The discovery is timely given the growth in drug-resistant infections which, the researchers say, kill two million people a year. Patients undergoing treatments that put stress on their immune systems are particularly vulnerable.

Fungi infect billions of people every year, but some scientists suggest this global burden is not fully recognised.