The gut microbiome – the ecosystem of bacteria living in us – appears to be weakened in those who have visited the hospital with COVID-19. New research, published in the journal Good, suggests that microbiome health could be related to the severity of the infection and the persistence of long-term systems, although more work is needed to understand the exact nature of the relationship.
Although the coronavirus is thought to be a respiratory disease, the discovery of the virus in patient fecal samples and intestinal cells has led scientists to believe that the gastrointestinal tract is somehow involved in the disease. Over the last decade, there has been growing evidence that the microbial community living in our digestive system plays a role in our overall well-being and health, and especially in the function of our immune system.
To further understand the link between the SARS-CoV-2 virus and the intestinal microbiome, the researchers analyzed stool samples from 100 patients with COVID-19 in two hospitals in Hong Kong. To find out more about COVID and intestinal ulcers, data up to 30 days after recovery are included.
The team found that fewer bacteria in the gut that are known to affect the immune system’s response to infection are present in patients admitted with COVID-19 than in those admitted for other diseases. A small number of these species are especially associated with the severity of the patient’s infection, and the number of these bacteria remained low in the patients up to 30 days after recovery.
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However, as this study was pure observation, the authors could not say with certainty whether the virus caused the changes, whether the gut microbiome determined the severity of COVID-19 or whether the effect was purely correlated – only that a link was found.
“We cannot rule out the possibility that the composition of the intestinal microbiota was a product of disease, clinical treatment and / or drugs,” said the study’s lead author, Professor Siev C Ng.
“However, the compositional signatures we observed include a path from mild to severe disease and the depletion of beneficial bacteria with immunomodulatory potential suggest that the intestinal microbiota is likely to be involved in the disease.”
Before you go out and start eating microbiome-enhancing foods – such as kimchi, blue cheese or baked beans – to try COVID-19 treatment, experts urge caution.
“Until it can be clearly demonstrated that altering the intestinal microbiome alters the risk of COVID-19, it would not be appropriate to propose measures to improve intestinal health to increase resistance to COVID-19,” explains Dr. Caitlin Wade, an epidemiologist at the University of Bristol. links between gut health and cancer-like diseases. “Much further and deeper research is needed to understand this complex relationship and draw significant conclusions.
How could the virus affect the gut microbiome?
“The ecosystem of bacteria living in human intestines has been the subject of intensive study for more than a decade,” said Professor Willem van Schaik, who researches human microbiomes and antibiotic-resistant bacteria at the University of Birmingham.
“Although the gut microbiome is generally healthy in healthy individuals, its composition can change, sometimes dramatically, through dietary interventions, exposure to antibiotics, and disease.”
Knowing this, the study authors controlled factors including antibiotic treatment and age. “After taking it [these factors into] account, a smaller number of two types of bacteria – Faecalibacterium prausnitzii i Bifidobacterium bifidum – they were still significantly associated with more serious symptoms of COVID-19 “, said Ng.
“We want to emphasize that the study does not have the power to discriminate whether the changes are due to the virus itself or a combination of factors.”
How could the connection between the gut and the coronavirus lead to a long COVID?
The team believes that the persistent microbiome imbalance observed in their study could contribute to the long-term symptoms of COVID seen in some people after they recover from SARS-CoV-2 infection. “We hypothesize that a lack of these beneficial species could contribute to multisystem inflammation syndromes after virus cleansing,” Ng said.
“It is a reasonable hypothesis that an abnormal population of microorganisms in the intestines could contribute to autoinflammatory and autoimmune disorders that occur during infection or occur later during long COVID,” said Prof. Graham Rook, emeritus professor of medical microbiology at University College London.
However, Rook advises that any changes in the composition of the intestinal microbiome could be secondary to the disease. “[It could even be] “The psychological stress caused by hospitalization due to COVID-19 will cause changes in the microbiota,” Rook said.
“I assume that the hypothesis will prove to be correct and will prove to be one of the reasons for the disproportionate susceptibility of individuals with low socioeconomic status, who for many reasons, especially due to poor nutrition, have suboptimal microbiota.”
What could this mean for COVID-19 treatment?
“It would be exciting if the transfer of the microbiota from appropriate donors could be used to treat long-term COVID, but more final studies will be needed,” Rook said.
This is exactly what Ng and her team plan to look at. “[We] “They are now investigating whether replacing these seemingly beneficial bacteria could improve a person’s response to SARS-CoV-2 infection and perhaps shorten recovery time,” Ng said.
“We are also conducting clinical trials to determine the effectiveness of the oral microbiome immunity formula in reducing weight and preventing long-lasting symptoms. Our other target populations are high-risk people, such as people with chronic diseases, because they seem to have a worse outcome when they are infected. “
The findings also have the potential for further research into coronavirus vaccines. “We will also conduct studies to determine how changes in the gut microbiota will affect the vaccine response,” Ng said.