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A common type of mold could infect people’s lungs

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A common type of fungus called Aspergillus fumigatus could become drug resistant. Smith/Gado/Getty Images Collection
  • An extremely common type of fungus found indoors and outdoors could damage the lungs of immunocompromised people.
  • These molds are becoming increasingly resistant to drugs, making infections harder to treat.
  • Genetic analysis of a new study reveals that the widespread presence of agricultural antifungals in the environment is the cause of this growing drug resistance.

The mushroom Aspergillus fumigatus is everywhere. Mold is so common indoors and outdoors that most people inhale and exhale some of it daily without any ill effects.

However, for approximately 10 to 20 million people worldwide with weakened immune systems, its spores remain in the lungs and, if they progress in aspergillosisthese spores can cause lung infections, allergic reactions and infections of other organs.

The preferred treatment for aspergillosis is the administration of azole antifungal drugs. However, in recent years the fungus has gradually become more resistant to these drugs.

Azole antifungals left in the environment from longtime agricultural use may be the cause of drug resistance, a new study by researchers at Imperial College London has found. Aspergillus fumigatus.

Imperial’s Dr Johanna Rhodes, who was the study’s lead author, says Imperial College London News“Increasingly, cases of aspergillosis seen in the clinic are resistant to first-line azole drugs.”

“Understanding the environmental hotspots and genetic basis for the evolution of fungal drug resistance requires urgent attention because resistance compromises our ability to prevent and treat this disease,” notes the study’s lead author, Dr. Professor Matthew Fisher.

“The prevalence of drug-resistant aspergillosis has risen from negligible levels before 1999 to 3-40% of cases today across Europe.”
—Professor Matthew Fisher

Added to the sense of urgency is a growing number of vulnerable people, especially since the pandemic.

“At the same time, more and more people may be sensitive to Aspergillus fumigatus due to the growing number of people receiving stem cell or solid organ transplants, undergoing immunosuppressive therapy, or suffering from lung disease or serious viral respiratory infections,” adds Professor Fisher. Among these respiratory infections is COVID-19.

The study is published in the journal Natural microbiology.

Azole antifungals are 14-alpha demethylase inhibitors. There are more than 25 different varieties of azoles, with which farmers have been protecting crops against fungal diseases for decades.

Dr Takahiro Takazonoassistant professor at Nagasaki University in Japan, who was not involved in the study, said Medical News Today:

“There are other classes of antifungals for filamentous fungi…However, the route of administration of these antifungals is intravenous only. Azoles are [the] only oral antifungal so far.

He also noted that there may be a new alternative to azoles currently in clinical trial.

The researchers collected 218 Aspergillus fumigatus isolates from 2005 to 2017 in England, Wales and Scotland. About 7 out of 10 molds, or 153 samples, came from 143 patients at five hospitals. The remaining 65 samples came directly from the environment.

Almost half, 48% or 104 samples, were found to be resistant to itraconazole, the most commonly used azole antifungal.

The remaining drug-resistant samples included 64, or 29%, that were resistant to voriconazole, with 21% resistant to posaconazole, two other azole antifungals.

More than 10%, or 23 environmental samples and 3 from patients, were resistant to two or more azole drugs.

To establish possible connections between the two sets of samples, the researchers extracted and sequenced the DNA of the moulds.

Genetic comparison of the samples revealed that six Aspergillus strains found in the environment had infected six patients.

The study describes their patient and environmental samples as “genetically very closely related.”

“The spores of Aspergillus are floating in the air everywhere,” Dr. Takazono said.

“[Aspergillus fumigatus spores] can be easily carried by the wind. Another possibility is that the spores (in the soil) attach themselves to agricultural produce and can spread to the daily life of an immunocompromised host.
— Dr. Takahiro Takazono

“We don’t know exactly how patients get these infections, whether they develop in the lungs while the infection is being treated, or whether the mold spores that infect them are drug resistant,” says Dr. Rhodes.

“Our study reveals that both routes of infection are possible and confirms concerns that pre-resistant mold spores in the environment can enter and infect people’s lungs, causing disease that is more difficult to treat.” he.

According to the study, the results demonstrate that “patients at risk were infected with isolates that pre-acquired their resistance to azoles in the environment” since research so far has not shown that patients transmitted their Aspergillus fumigatus to the environment.

A new type of resistance

Genetic analysis divided the samples into two distinct groups or “clades”. Clade A contained 123 isolates and Clade B 95. About 80% of Clade A samples were drug resistant, while 87% of Clade B samples were not.

However, as distinct as the two clades are, the researchers found indications that they could swap genetic material, allowing for new drug-resistant genetic combinations.

“These results indicate the existence of novel resistance mechanisms with an underlying polygenic base and show that a better understanding [of] the role of accessory genes in generating drug-resistant phenotypes is needed,” the authors write.