The intestinal flora can influence the severity and response to Covid-19

The variety and quantity of bacteria present in the intestine -microbiome-, can influence the severity of covid-19, but also the response of our immune system to infection. This is suggested by research published in the journal “Gut” which also indicates that imbalances in the composition of the microbiome may also be involved in the persistence of inflammatory symptoms, called persistent covid.

In another work, published in «mBio», it is claimed that a bad Gut health negatively affects the prognosis of covid-19. This review states that intestinal dysfunction can exacerbate the severity of the infection by allowing the virus to access the surface of the digestive tract and internal organs. These organs are vulnerable to infection because have generalized ACE2, a target protein of SARS-CoV-2, on the surface.

Although COVID-19 is considered primarily a respiratory disease, evidence suggests that the gut may also play a role. Because the gut is the body’s largest immune organ, and its resident organisms are known to influence immune responses, researchers are studying whether the gut microbiome might also affect the immune system’s response to infection.

In the study published in “Gut”, researchers from the Chinese University of Hong Kong obtained blood and stool samples and medical records from 100 patients hospitalized for confirmed COVID-19 and 78 people without COVID-19 who participated in a study of microbiome prior to the pandemic.

Analysis of the 274 stool samples showed that the composition of the gut microbiome differed significantly between patients with and without COVID-19, regardless of whether they had been treated with medications, such as antibiotics.

This suggests that the gut microbiome could influence the immune system’s response to COVID-19 infection and potentially affect the severity and outcome of the disease, the researchers say.

Thus, COVID-19 patients had far fewer species that can influence the immune system response, such as Bifidobacterium adolescentis, Faecalibacterium prausnitzii, and Eubacterium rectole.

The lower amounts of F. prausnitzii and Bifidobacterium bifidum were associated with the severity of the infection after taking into account the use of antibiotics and the age of the patient.

Furthermore, the amount of these bacteria remained low in the samples collected up to 30 days after the infected patients had shed the virus.

Covid-19 infection causes the immune system to produce inflammatory cytokines in response. In some cases, this response may be excessive – cytosine storm – causing widespread tissue damage, septic shock, and multi-organ failure.

Analysis of the blood samples showed that the microbial imbalance found in COVID-19 patients was also associated with elevated levels of inflammatory cytokines and blood markers of tissue damage, such as C-reactive protein and certain enzymes.

This suggests that the gut microbiome could influence the immune system’s response to COVID-19 infection and potentially affect the severity and outcome of the disease, the researchers say.

Researchers conclude: “Boosting beneficial gut species depleted in COVID-19 could serve as a novel avenue to mitigate severe disease, underscoring the importance of controlling patients’ gut microbiota during and after COVID-19” .

In the study published in “mBIO”, coordinated by the microbiologist Heenam Stanley Kim, of the University of Seoul (Korea), the emerging evidence that suggests that poor intestinal health adversely affects the prognosis of covid-19 was examined.

Some researchers point out that unhealthy gut microbiomes may be one reason why some people have such serious infections.

It has been shown that people with previous pathologies -hypertension, diabetes and obesity-, or of advanced age have a greater risk of severe covid-19. But both factors, advanced age and chronic conditions, are also related to an altered gut microbiota.

This imbalance can affect the integrity of the gut barrier, Kim believes, which can allow pathogens to more easily access the cells of the gut lining.

So far, the link between gut health and covid-19 prognosis has not been proven. Some researchers point out that unhealthy gut microbiomes may be one reason why some people have such serious infections.

But studies so far point to a complicated relationship. Thus, a study carried out in Singapore in symptomatic covid-19 patients, for example, found that approximately half had a detectable level of the coronavirus in fecal tests, but only half of those experienced gastrointestinal symptoms. That study suggests that even if SARS-CoV-2 reaches the gastrointestinal tract, it may not cause problems.

But recent work has found reduced bacterial diversity in intestinal samples from COVID-19 patients, compared to samples from healthy people. The disease has also been linked to the depletion of beneficial bacterial species and the enrichment of pathogens.

Kim’s team began looking at the studies after realizing that rich countries with good medical infrastructure, such as the US and Western European nations, are among the hardest hit by the virus. The “Western diet” is low in fiber and “a diet deficient in fiber is one of the main causes of altered gut microbiomes.”

Although the pathogenesis of COVID-19 is still not fully understood today, Kim believes that if future studies show that gut health affects the prognosis of COVID-19, doctors and researchers should explore that connection to improve. strategies to prevent and control the disease. Eating more fiber can reduce a person’s risk of serious illness. And fecal microbiota transplantation could be a treatment worth considering for patients with the worst cases of COVID-19, “he says.

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