There is an urgent need for better ways of infection control in hospitals. A recent study investigated if certain herbicides could help prevent fungal infections.
Worldwide, fungal infections kill almost 2 million people every year. About 10% of patients in hospital intensive care units will acquire a fungal infection during their stay. Infected patients are twice as likely to die compared to non-infected patients. Furthermore, more patients are being infected with strains of fungus that are resistant to current antifungal drugs. There is, therefore, an urgent need for new drugs that could help with infection control in hospitals.
Fungi have many genetic and metabolic similarities to plants. Scientists believe that certain commercial herbicides, designed to kill plants, may be able to kill fungi without harming people or animals. A group of Australian and Chinese researchers have been testing a family of herbicides that work by inhibiting a specific enzyme that both plants and fungi need to survive. This enzyme isn’t used by humans and other animals, so this herbicide should kill fungi without hurting patients. They recently published their results in the Proceedings of the National Academy of Sciences.
A herbicide that kills fungi
The researchers started by comparing the fungi-killing ability of different types of herbicides. One commercially available herbicide, chlorimuron ethyl, was particularly effective at preventing the growth of many different types of fungi in laboratory Petri dishes. Combining the herbicide with the commonly used anti-fungal drug itraconazole was even more effective. The researchers then tested the safety of the herbicide by injecting it into mice. It caused no ill effect in the mice, even at high concentrations.
Can it clear a fungal infection in mice?
To test this potential drug further, the researchers checked to see if it could clear a Candida albicans infection in mice. Candida is one of the most common causes of fungal infections in hospital intensive care units. It also causes yeast infections (fungi that grow as individual cells, like Candida, are called yeasts) and thrush.
Without treatment, a Candida albicans infection will kill any mouse it infects. However, an injection of the herbicide allowed about half of the infected mice to recover and survive. The herbicide also decreased the amount of live fungus in most of the mice’s organs.
A long road ahead
There are still many years to go before this herbicide could ever be used as a drug in humans. To start with, more animal testing is needed to determine if it is effective against other types of fungal infections. It would then need to be tested in humans for safety and effectiveness and to determine if it can be used with existing anti-fungal drugs. Despite all this remaining work, the researchers believe that this type of drug has great promise to treat fungal infections in humans and to help with infection control in hospitals.
Written by Bryan Hughes, PhD
- Garcia, M. D., Chua, S. M. H., Low, Y.-S., Lee, Y.-T., Agnew-Francis, K., Wang, J.-G., Nouwens, A., Lonhienne, T., Williams, C. M., Fraser, J. A. &Guddat, L. W. Commercial AHAS-inhibiting herbicides are promising drug leads for the treatment of human fungal pathogenic infections. Proceedings of the National Academy of Sciences 115, E9649-E9658 (2018)
- Vincent, J., Rello, J., Marshall, J. & et al. International study of the prevalence and outcomes of infection in intensive care units. JAMA 302, 2323-2329 (2009)