Cladosporium is a genus of ubiquitous environmental fungi that has been reported to induce asthma and colonize the airways of both healthy and asthmatic individuals. A study presented at the CHEST annual meeting hosted by the American College of Chest Physicians explored the relationship between the prevalence of Cladosporium in the sputum of asthmatic individuals and control of their asthma.
In this exclusive MedPage Today video, lead author Amjad N. Kanj, MD, from the Mayo Clinic in Rochester, Minnesota, explains the study design and clinical significance of the results.
Following is a transcript of his remarks:
We used to think that lungs were sterile, but with the development of culture independent techniques, we now know they host a diverse community of microorganisms, including fungi. And the particular fungal genus that we commonly encountered while studying the lung microbiome of patients with asthma was Cladosporium.
And that caught our attention because of the well-known association of Cladosporium in the environment with asthma. And there have been studies reporting more Cladosporium in homes of patients with asthma. Other studies correlating high levels of Cladosporium during thunderstorms towards asthma control — the so-called thunderstorm asthma. But we were not aware of studies of the abundance of Cladosporium residing in the lungs of patients with asthma and its relation to their asthma control.
So to answer this question, we collected sputum samples from 24 patients with asthma from our asthma clinic. The patients had also completed an Asthma Control Test (ACT) at the time of sputum collection. And we used the median test score of all the patients, which was 17.5 in our case, to divide them into two groups. Those with an ACT score higher than the median, and we called this group the worse asthma control. And then those with an ACT score higher than the median, and we called this group the better asthma control. We then processed their sputum, extracted the DNA, and sequenced it for fungi.
So this is what we found. Cladosporium was the third most prevalent fungi in the lungs and was identified in 16 patients out of the 24 patients we had. Right off the bat, it was clear that Cladosporium was much more prevalent in those with worse asthma control. And this was our main finding. In fact, when we looked at the individual patient level, of the 16 patients who had Cladosporium, 11 were in the group with worse control.
And both groups were not different in terms of baseline characteristics, other clinical and laboratory characteristics, and even in terms of how diverse the fungal community was as measured by the Shannon Diversity Index.
So despite the small sample size, we had a strong signal of difference in Cladosporium abundance between the groups. We also looked at some potential confounders, like the season during which the sample was collected, or whether the Cladosporium could be residing in the oral cavity of these patients and then contaminating the sputum or whatnot. But findings were non-revealing. In fact, only three of the 24 patients had Cladosporium detected in their oral cavity, which is very little I guess.
So just to summarize things here, so Cladosporium was more abundant in the lungs of asthmatics with worse symptom control. Now obviously studying this at a larger scale is important here with cross-sectional studies, we tend to run into the egg and the chicken dilemma. So also studying this in animal models and attempting to elucidate or clarify some of the biologic mechanisms behind this observation is also important.
And in terms of clinical implication, I guess the main question here would be whether there could be a subset of patients with uncontrolled asthma who would benefit from reducing or eliminating the Cladosporium from their lung.