Increased Cladosporium abundance associated with poor asthma control
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Key takeaways:
- Cladosporium induces asthma.
- The fungus was more abundant in the sputum of patients with Asthma Control Test scores of 17 and lower.
- Interventions designed to reduce exposure may be beneficial.
HONOLULU — Cladosporium was more abundant in the lungs of patients with poor asthma control compared with patients who had better control, according to a poster presented at the CHEST Annual Meeting.
Interventions that reduce exposure to the fungi in the environment may improve outcomes, although more research is needed, Amjad N. Kanj, MD, MPH, a pulmonary and critical care fellow at Mayo Clinic in Rochester, Minnesota, said during his presentation.
“While investigating the airway mycobiome of patients with asthma, we frequently encountered Cladosporium species in significant prevalence,” Kanj told Healio.
“This captured our attention because Cladosporium is a spore-forming mold known to be allergenic, and environmental exposure to it can exacerbate asthma symptoms,” he continued.
Previous studies have indicated that Cladosporium, a ubiquitous environmental fungi, induces asthma and colonizes the airways of healthy individuals and of individuals with asthma, Kanj and colleagues wrote in their abstract.
Cladosporium has been found in higher concentrations in the homes of individuals with asthma as well, the researchers continued, but the relationship between the relative abundance of this fungi in sputum and asthma control has not been investigated.
“This led us to question: If environmental exposure to Cladosporium can worsen asthma, would there be an association between Cladosporium residing in the lungs of asthma patients and their degree of asthma control at the time of sputum collection?” Kanj said.
Study design, results
The researchers collected sputum samples from 24 adults with asthma (median age, 57 years; interquartile range [IQR], 46-69; 18 women), most of whom were never smokers, attending the asthma practice at Mayo Clinic between 2020 and 2022. The researchers manually extracted DNA from these patients using the QIAamp DNA Mini Kit (Qiagen) and sent it for fungal ITS2 sequencing.
The cohort had a median score of 17.5 (IQR, 15-19) on the Asthma Control Test (ACT). Researchers divided the cohort into those with better control (ACT 18; median age, 57 years; 67% women) and those with worse control (ACT 17; median age, 55 years; 83% women).
Researchers used the Mann-Whitney U test to compare relative abundances of Cladosporium between these ACT groups.
The most common Amplicon Sequence Variants in the sputum samples belonged to Candida, Malassezia and Cladosporium, which constituted 6.5% (median, 1.8%; IQR, 0%-66.5%) of the fungal communities across all the samples.
Also, Cladosporium appeared more prevalent among the patients with worse control (median, 4.2%; IQR, 0%-69.4%) compared with the patients with better control (median, 0%; IQR, 0%-36.1%.
There were no significant differences in the abundance of Cladosporium based on season, nor were there any associations with antibiotic or systemic glucocorticoid use or with risks for asthma exacerbations in the previous year, according to the researchers.
“We observed a similar trend with Alternaria, but it did not meet statistical significance given it was less prevalent among our patients,” Kanj said, adding that it was only detected in eight patients. “This was interesting considering Alternaria tends to coexist with Cladosporium in the environment.”
Conclusions, next steps
Based on these findings, the researchers called the association between the increased relative abundance of Cladosporium in the lungs of patients with poor asthma control at the time of sputum collection significant.
“Our understanding of the lung mycobiome remains limited, despite well-established knowledge identifying certain environmental fungi as potent asthma triggers,” Kanj said.
Kanj called their findings significant because they establish a link between the prevalence of a specific spore-producing mold, Cladosporium, in the lungs and asthma symptom control.
“This suggests a possible role of lung-residing microorganisms in influencing and aggravating asthma and may open new avenues for mitigating uncontrolled asthma,” Kanj said.
More studies are necessary to establish how much the fungus contributes to uncontrolled asthma in the community, determine the effectiveness of interventions that may reduce environmental exposure and develop potentially beneficial targeted therapies, the researchers said.
“Despite the small sample size, we observed a strong signal and are interested in exploring this further on a larger scale,” Kanj said.
Establishing a link between environmental exposure to specific molds and their prevalence in the lungs of patients with asthma will be very informative, he continued.
“One approach could involve analyzing the mycobiome of air and dust in the homes of asthma patients in correlation with the study of their sputum mycobiome,” he said.
Most significantly, Kanj added, this study suggests that there could be a subset of patients with uncontrolled asthma who might benefit from the elimination of Cladosporium from their lungs.
“It is uncertain whether the presence of Cladosporium in patients’ lungs is linked to environmental exposure,” Kanj said.
Nevertheless, he continued, it may be useful to remind patients with asthma of the risks associated with living or working in areas with high humidity, excess moisture and poor ventilation, which are conducive environments for mold growth.
“In turn, providers may want to advise patients who live or work in such areas about implementing practical strategies such as ensuring proper ventilation and eradicating sources of dampness,” Kanj said.