A drug-resistant fungus is spreading from the environment and infecting people with lung conditions or weakened immune systems, a new study suggests.
The researchers found six cases of people infected with a drug-resistant form of a fungi called Aspergillus fumigatus – an environmental mould that can cause fungal lung disease – that could be traced back to spores in the environment.
While people with healthy lungs are usually able to clear spores that have been inhaled, sometimes people with lung conditions or weakened immune systems cannot do this.
This means the spores may remain in the lungs, causing an infection called aspergillosis.
Understanding the environmental hotspots and genetic basis of evolving fungal drug resistance needs urgent attention, because resistance is compromising our ability to prevent and treat this disease
Professor Matthew Fisher
Aspergillosis affects 10-20 million people worldwide, and while the infection is usually treated with an antifungal drug, emerging resistance to these drugs has been reported, according to the Imperial College London researchers.
They suggest this resistance has evolved because of the widespread agricultural use of azole fungicides.
Medicines known as azole drugs that work in a similar way are the first-line treatment for patients infected with the Aspergillus fumigatus mould.
Therefore the exposure of the fungus to azole fungicides in the environment means it is often in a drug-resistant form even before it encounters the people it infects.
The researchers are calling for greater surveillance of Aspergillus fumigatus in the environment and the clinic to help understand the risk it poses.
Senior author, Professor Matthew Fisher, from Imperial’s School of Public Health, said: “Understanding the environmental hotspots and genetic basis of evolving fungal drug resistance needs urgent attention, because resistance is compromising our ability to prevent and treat this disease.”
He added: “The prevalence of drug-resistant aspergillosis has grown from negligible levels before 1999 to up to 3-40% of cases now across Europe.
“At the same time, more and more people might be susceptible to Aspergillus fumigatus infection because of growing numbers of people receiving stem cell or solid organ transplants, being on immunosuppressive therapy, or having lung conditions or severe viral respiratory infections.”
In the study, the researchers isolated 218 samples of Aspergillus fumigatus from across England, Wales, Scotland and Ireland between 2005 and 2017.
Around seven in 10 samples were from people infected (153 samples from 143 patients in five hospitals), and the rest were from the environment (65) – including from soil, compost, plant bulbs, the air and other sources.
Upon analysing these samples, the researchers found six strains of Aspergillus fumigatus that existed in the environment which had infected six patients.
The researchers say that the genetic similarities indicated the fungus had spread from the environment to the patient.
Lead author, Dr Johanna Rhodes, from Imperial’s MRC Centre for Global Disease Analysis within the School of Public Health, said: “Increasingly, the cases of aspergillosis seen in the clinic are resistant to first-line azole drugs.
“However, we’ve not been sure how patients are acquiring these infections – whether they develop in the lungs during treatment for the infection, or whether the mould spores that infect them are drug-resistant in the first place.
“Our study finds that both routes of infection are possible and confirms concerns that pre-resistant mould spores in the environment are able to enter and infect people’s lungs causing harder-to-treat disease.”
According to the study, of the 218 samples, 106 samples were resistant to at least one of the first-line azole drugs used in the clinic.
More than 10% of samples (26, including 23 environmental samples and three from patients) were resistant to two or more azole drugs, the study found.
The study, funded by the Natural Environment Research Council, the Wellcome Trust, Gilead Sciences and the Medical Research Council, is published in Nature Microbiology.