The variety and volume of bacteria in the intestines may influence the severity of COVID-19, according to new research from Hong Kong.
The complex system of billions of bacteria residing in the gut is commonly referred to as the microbiome. The term not only refers to the microorganisms themselves, but the entire “theater of activity” they are involved in.
The adult human body should be populated by about three pounds of healthy bacteria; however, it is common for an unhealthy gut to be populated by up to ten pounds of bad bacteria.
The researchers noted the gut is “the largest immunological organ in the body”—and as such, they wanted to find out if the gut microbiome might also affect the immune system response to COVID-19 infection.
To conduct the study researchers obtained blood and stool samples and medical records from 100 hospital patients with laboratory-confirmed COVID-19 infection, and from 78 people without COVID-19. The COVID-free patients were taking part in a microbiome study before the pandemic started.
To characterize the gut microbiome, 41 of the COVID patients provided multiple stool samples while in the hospital. Next, 27 of the patients provided stool samples up to 30 days after they were cleared of of SARS-CoV-2 (the virus responsible for COVID-19).
Analysis of all stool samples showed that the make-up of the gut microbiome differed significantly between patients with and without COVID-19, irrespective of whether they had been treated with drugs.
COVID patients had higher numbers of cell-destroying bacterial species—including Ruminococcus gnavus, Ruminococcus torques and Bacteroides dorei—than the study participants who were free of infection.
The COVID patients also had far fewer of the “good” species that are known to influence immune system response—such as Bifidobacterium adolescentis, Faecalibacterium prausnitzii and Eubacterium rectale.
Healthy microbiome vital
Another noteworthy finding reported by the researchers was that the numbers of beneficial bacteria remained low in the samples collected up to 30 days after infected patients had cleared the virus from their bodies.
In light of reports that a subset of recovered patients with COVID-19 experience persistent symptoms, such as fatigue, dyspnoea [breathlessness] and joint pains, some over 80 days after initial onset of symptoms, we posit that the dysbiotic gut microbiome could contribute to immune-related health problems post-COVID-19,” the researchers wrote.