The Gut Microbiome Composition and COVID-19 Related Disease Severity
The gut microbiome refers to a group of commensal or symbiotic bacteria that make up the composition of microorganisms in the human intestines. At any given period in time, most healthy adults may have up to 1,000 different species of bacteria that inhabit the digestive tract.(1) Most of these fall into the Bacteroidetes or Firmicutes phyla, which include a variety of beneficial species that play an important role in human well-being by aiding in digestion, providing beneficial vitamins, supporting immune health, and preventing certain types of cancers. Studies show an imbalance in the gut microbiome can play an important role in certain disorders such as obesity, high cholesterol, high blood sugar leading to Type 2 diabetes, arthritis, and more. (1) Consequently, due to the range of disease severity observed in patients with confirmed SARS-CoV-2 infection, researchers looked for clues in the gut microbiome composition to determine the impact on the severity of COVID-19 symptoms.(2)
A two-hospital cohort study was designed to examine blood, stool, and other evidence from health records for contributing factors from patients with laboratory confirmed SARS-CoV-2 infection. Testing occurred up to a maximum of 30 days after a patient was cleared of the virus, and used a shotgun sequencing approach for total DNA extracted from stool. (2) For comparison, inflammatory cytokines, chemokines, and peptides were also measured from patient blood samples, and patients were separated into four severity groups based on their disease symptoms. (2)
What researchers found from the study was an overall change in the composition of the gut microbiome in SARS-CoV-2 infected patients compared to non-infected individuals. Data also suggested the change was unrelated to whether patients required medication, but alterations in the microbiome appeared concordant with disease severity.(2) Many of the previously documented commensal bacteria known to inhabit the gut and modulate the immune response in healthy adults were dramatically underrepresented in infected patients, and continued to remained low even after recuperation and confirmed negative infection. (2)
Not surprisingly, results from the study found a correlation between the gut microbiota composition, levels of inflammatory cytokines in blood, and the severity of COVID-19 symptoms. These initial results suggest the gut microbiome may modulate the host immune response to COVID-19 infection. More research is needed to determine how this interaction contributes to the inflammatory response, and the mechanisms which may aid in patient recovery.