The bacteria of our gastrointestinal system, allies against COVID-19

By Sonia Villapol, Houston Methodist Research Institute

The great danger of the coronavirus lies in the loss of control due to its implacable transmissibility. Especially by people who do not show respiratory symptoms or fever, so they do not know if they are infected: the so-called "silent" transmitters. Gastrointestinal symptoms can play a critical role in stopping the spread.

During the course of COVID-19 several phases take place. 60% of those infected were found to have intestinal problems such as diarrhea, vomiting, or abdominal pain in the early stages of the disease. This days before respiratory symptoms or even pneumonia are detected.

When infected people have intestinal symptoms, it is not suspected to be due to coronavirus infection. Therefore, they are not tested. This represents a huge risk factor in transmissibility.

Gastrointestinal symptoms and changes in flora associated with COVID-19. Royalty-free Illustration, FAL

A symptom for each phase

At the beginning of the disease, the virus begins to replicate and infect cells in different systems of the body. This can cause intestinal dysfunction, changes in bacterial flora, and acute systemic inflammation.

As the disease progresses, the virus does not need to replicate, and the most powerful inflammatory cascade bursts, accompanied by respiratory problems and fever. People who had intestinal symptoms in the early stages were those who developed more complications in later stages.

The reasons why SARS-CoV-2 causes more pathologies in some people than others remain unknown. Still, there are patients who manage to clear the virus without developing symptoms, suggesting that a strengthened immune system may give us the key to understanding and overcoming the viral infection.

In this context, identifying the non-respiratory symptoms associated with COVID-19 as soon as possible could stop the spread.

Alterations in the microbial flora

The primary gateway for SARS-CoV-2 invasion is angiotensin-converting enzyme 2 (ACE2) receptors that are expressed in the lungs, but are also found in the intestines.

The entry of the coronavirus produces an increase in inflammation that causes alterations in the intestinal flora. These can aggravate the so-called systemic cytokine storm or hyperinflammation in the most severe patients. Most COVID-19 comorbidities such as obesity, hypertension, cardiovascular disease, diabetes, and old age are associated with decreased microbial diversity.

The less diversity, the greater the inflammatory response. Therefore, we would expect a worse prognosis for COVID-19. If we can identify which bacteria orchestrate the course of the disease, we could predict the severity and prognosis of COVID-19.

A couple of studies with a very small group of hospitalized patients identified that the coronavirus altered the intestinal microbes of the patients in relation to the severity of COVID-19.

Similar studies are also necessary in the asymptomatic or mildly symptomatic population. In our laboratory we try to identify which intestinal bacteria in SARS-CoV-2 infected are related to inflammatory markers and viral load. If we can establish which bacteria are associated with the symptomatology, we could interfere and modify the abundance of these bacteria to protect ourselves from the severity of COVID-19.

Diet and probiotics

It is possible to modify the intestinal flora by changing the diet or using specific probiotics. Family bacteria Bifidobacterium or Lactobaccillus reduce inflammation. Others, like Clostridium, they can act as possible pathogens.

If we promote an adequate nutritional state, we can improve the immune response in the early stages of infection. This would depend on the intake of dietary fiber, which reduces the risk of infection. Furthermore, vitamins A, D, C or E and omega-3 fatty acids favor intestinal bacteria to ferment by-products that help the anti-inflammatory response.

Once we determined which bacteria are associated with COVID-19 severity, we could design treatments or diets to modify them in a matter of days. It may be possible to reduce the inflammatory response by modifying the intestinal flora to protect us from the more serious consequences of COVID-19. By increasing bacterial diversity, we protect ourselves not only from viral infections, but also against other health problems, including mental health.

Sonia Villapol, Assistant Professor, Houston Methodist Research Institute

This article was originally published in The Conversation. Read the original.