Resistance to antifungal treatments is growing, according to a report published in Science journal last week. A team of scientists from Imperial College London and the University of Exeter said that the recent emergence of pathogenic fungi is unprecedented and could lead to a much more widespread outbreak of disease.
The researchers said that the over application of existing antifungal drugs - in particular those belonging to the azoles class - in both healthcare and agriculture was a key issue behind the problem. This has enabled resistant strains to develop rapidly, leading to current treatments becoming less effective.
Currently, crop-destroying fungi account for 20% of yield losses world wide. The use of antifungal treatments on plant pathogens has created many fungicide-resistant variants due to cropping practices being largely monoculture (single crop).
Also, fungal effects on human health are rapidly increasing. The global mortality rate for fungal infections has now overtaken breast cancer and malaria.
When are antifungal treatments used?
A healthy immune system can easily deal with fungi, and does so regularly as they are present in much of our everyday environment (such as in the air we breathe, in our bodies, in some foods we eat). The presence of different types of fungi helps to counterbalance each other.
It’s when the balance of fungi either in the body or on our skin becomes upset that we develop an infection; and in some cases, the immune system may not be able to tackle it on its own. This is when antifungal medicine is typically administered.
Fungal infection numbers are increasing in people affected with HIV, the elderly population and patients in hospital. This translates to an increased risk of contracting a fungal infection in these groups.
Under the radar
It’s well-known that bacteria resistance to antibiotics has been increasing for some time. However, the threat of antifungal resistance is a lesser-known one.
The continued growth in the human population has led to more intensive agricultural methods to meet commercial demand. Crops are often treated with generic pesticides, and this has inadvertently improved the defences of the fungi.
Resistant fungal pathogens have then been able to spread themselves far more freely due to global trade, and ‘swap’ resistant traits with other fungi.
Professor Matthew Fisher from the School of Public Health at Imperial College London described the problem as ‘under-appreciated and under-recognised’, and a pressing issue which needed to be addressed.
‘Alongside drug discovery and new technology to tackle fungal pathogens,’ he said, ‘we urgently need better stewardship of existing antifungals to ensure they are used correctly and that they remain effective.’
One of the main fungicides used around the world, azoles are believed to account for a quarter of antifungal pesticides.
They are also frontline drugs for both humans and animals, and their extensive use is increasing antifungal resistance as non-resistant strains die off.
Fungi that are resistant to all known treatments are emerging. Candida auris, which was first discovered in Japan in 2009, is a notable example. It is now responsible for many hospital-acquired invasive infections around the world and can survive decontamination protocols.
Tackling the problem
So what can be done to combat the issue?
The research points to an over-reliance on chemical control and a need to develop an approach that isn’t solely reliant on chemicals for fungicides. It also suggests that there should be a more targeted use of antifungals in order to maintain the effectiveness of the drugs; and that the research and development of new treatments, particularly those which target the genes of the fungi to stop them from spreading, are needed.