Fewer fungi types in lungs associated with more severe ARDS
Lower fungal alpha diversity in the lungs of patients with acute respiratory distress syndrome was associated with increased disease severity, researchers reported at the virtual European Respiratory Society International Congress.
Until now, research has concentrated on the effects of bacteria on human health, in part because the microbiome is primarily composed of bacteria and there are difficulties in extracting enough fungi to study, according to Noel Britton, MPH, PhD candidate at the University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center.
“Research into the lung mycobiome is very much in its infancy,” Britton told Healio.
It is known that fungi can be involved in activating and regulating the human immune system, according to Britton.
“There are no known therapies for the successful treatment of ARDS and very little is known about why some patients have a hyper-inflammatory response. The diversity of the microbiome, and specifically fungi, may play an important role in understanding why some patients develop ARDS and some do not,” she said in a press release.
Researchers enrolled 202 patients on mechanical ventilation who had or were at risk for ARDS from October 2011 to September 2019. Of those, 21% had an ARDS diagnosis, the mean age was 50 years and 61% were women. The researchers collected endotracheal aspirates within 48 hours of patient intubation and used extracted DNA to perform fungal rRNA gene sequencing.
“We identified about 100 different types of fungi in the lungs of mechanically ventilated, critically ill patients. The diversity was quite low in all of the samples, but in samples in which a single species dominated, the diversity was very low. A large number of patients had samples that were dominated by a single fungal species from the Candida type; this made up more than 50% of the fungi present in these samples and it is known to be involved in causing disease in humans,” Britton said in the release.
The researchers observed lower fungal alpha diversity in patients with ARDS compared with those without ARDS, but not in patients at risk for ARDS. In the patients with ARDS, shock (P = .03), sepsis (P =.03) and a sequential organ failure assessment score of 5 (P = .02) were associated with lower fungal diversity.
Decreased diversity in these patients was associated with increased lung injury prediction scores (P= .05), lower plateau pressures (P = .03), vasopressor use (P = .01) and elevated plasma pentraxin-3 (P = .01).
“Moving forward we will work to identify specific mycobiome signatures and/or specific species associated with clinical and patient-centered outcomes in critical illness and ARDS,” Britton told Healio. “We will focus our efforts on understanding the impact of mycobiome variations on the host immune and inflammatory response. We are also very interested in the relationship and potential interaction of bacteria and fungi on each other and on the host immune and inflammatory response.”
Moreover, to the best of the researchers’ knowledge, none of the patients in this study had COVID-19. However, enrollment continues throughout the pandemic and a future analysis will look at patients with confirmed COVID-19, according to the researchers.