Higher ambient temperatures can cause mutations in fungi that lead to increased infectivity, more aggressive growth, or resistance to multiple antifungal drugs.
Microbiologist examines mold and fungal cultures in petri dishes.
Public health officials have long been concerned that rising global temperatures could make mold more harmful to humans. Sure, some people get ringworm or nail infections, and some women get repeated yeast infections, but other than these cases, yeast infections are not exceptionally problematic. However, this is changing.
An international team of medical researchers and infectious disease specialists based in China worked with a researcher from Singapore and another researcher from Canada, and together they found disturbing evidence suggesting that as the planet warms, fungi could become more dangerous to humans.
Normally, mammals are naturally protected from most fungal infections because fungi are cold-adapted organisms that grow best at temperatures cooler than those in and on the bodies of mammals. As a result, fungi cause far fewer diseases in mammals than bacteria and viruses. But infectious disease experts have warned that fungi have the potential to adapt to rapidly warming climatic temperatures and so could reach a point where they can life in and on the human body.
To see if this transition is already happening, researchers in China looked for fungal infections in patients in 96 hospitals in that country between 2009 and 2019. Among the thousands of pathogenic fungi they isolated and examined, they found one fungus that had never been discovered before. reported to infect humans. The pathogen, Rhodosporidiobolus fluvialiswas isolated from the blood of two unrelated patients treated in intensive care for serious underlying diseases: an 85-year-old woman from Tianjin who died in 2016 and a 61-year-old man from Nanjing who died in 2013. The pathogen was resistant to the two main drugs used to treat potentially fatal fungal infections in humans, caspofungin and fluconazole.
To further characterize this fungal pathogen and demonstrate that it could infect mammals, the researchers injected it into laboratory mice with compromised immune systems. Surprisingly, the fungus thrived and some fungal cells even mutated into a more aggressive form.
When investigators investigated the cause R. fluvialisDue to the increased pathogenicity, they found that cells grown at 37°C (human body temperature) developed mutations 21 times faster than cells grown at 25°C. The researchers also discovered that R. fluvialis developed drug resistance much more quickly when grown at 37°C and exposed to another common antifungal drug, amphotericin B.
This is very worrying. Given the increasing use of immunosuppressive medications in recent decades and the ongoing HIV epidemic, there are increasing numbers of immunocompromised people in the general population who are at increased risk for fungal infections. In addition, because fungi undergo increased mutation rates in warmer environments – including the higher body temperatures of mammals – this could cause mutations in fungi to make them more infectious and resistant to drugs.
Consistent with this finding, epidemiologists have reported that many new fungal diseases are emerging in humans, and that at least some of these new pathogens are already drug resistant.
These are unexpected findings and point to potentially disastrous consequences for the health of humans and other mammals if the planet continues to warm.
Source:
Jingjing Huang, Pengjie Hu, Leixin Ye, Zhenghao Shen, Xinfei Chen, Fang Liu, Yuyan Xie, Jinhan Yu, Feng-yan Bai, Yingchun Xu & Linqi Wang (2024). Drug resistance and hypervirulence in a human fungal pathogen are enabled by mutagenesis induced by mammalian body temperature, Natural microbiology | doi:10.1038/s41564-024-01720-y
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