Microbiome ‘profiling’ can help identify those at risk for long COVID

The composition of the gut microbiome may be linked to a person’s risk of developing ‘long COVID’ several months after initial infection with SARS-CoV-2, the virus responsible for COVID-19 infection, suggests a research published online in the journal Intestine.

Microbiome ‘profiling’ could help identify those most likely to develop the disease, the researchers suggest.

Post-acute COVID-19 syndrome, nicknamed “long COVID”, is characterized by complications and/or persistent symptoms weeks and months after the initial infection with COVID-19.

It is relatively common, with up to 3 in 4 people reporting at least one symptom 6 months after recovering from COVID-19 infection. Fatigue, muscle weakness and insomnia are the most commonly reported symptoms.

An exaggerated immune system response, cellular damage, or the physiological consequences of severe illness can contribute to the development of long COVID. But it’s unclear exactly what causes it, or why some people seem to be more susceptible, researchers say.

A growing body of evidence has implicated the gut microbiome – the trillions of bacteria, fungi and other microbes that inhabit the digestive tract – in the severity of COVID-19.

And since the gut plays a major role in immunity, a disordered immune response to COVID-19 infection, induced by resident microbes, can also affect the recovery process.

The researchers therefore wanted to know if the composition of the intestinal microbiome could be linked to a long COVID, defined as at least one symptom persisting 4 weeks after the elimination of SARS-CoV-2 from the body.

They followed changes in the gut microbiome of 106 patients with varying degrees of COVID-19 severity, treated at 3 different hospitals between February and August 2020, and in a comparison group of 68 people who did not have COVID-19. 19, during the same period. period.

They did this by analyzing stool samples from the participants. Among the 106 patients with COVID-19, stool specimens were collected at admission (68), then again after 1 month (64) and after 6 months (68). Stool samples were also collected from 11 patients 9 months later.

The researchers checked for the presence of the 30 most frequently reported long COVID symptoms 3 and 6 months after the initial COVID-19 infection. Aerobic capacity and endurance, an indicator of long COVID, were also measured in a 6-minute distance walking test.

The average age of patients infected with COVID-19 was 48 years old; just over half were women. Most (81%) had mild to moderately severe infection; 25 were treated with antibiotics.

Long COVID was reported in 86 (81%) of these patients at 3 months and in 81 (76.5%) at 6 months. The most common symptoms at 6 months were fatigue (31%), memory impairment (28%), hair loss (22%), anxiety (21%) and sleep disturbance (21%). ).

There were no significant differences in potentially influencing factors, such as age, sex, prevalence of underlying conditions, use of antibiotics or antiviral drugs, or severity of COVID-19 between patients with and without COVID long, 6 months after initial infection.

Among the 68 patients with COVID-19 whose stool samples were analyzed at 6 months, 50 had long COVID.

While initial viral load was not associated with long COVID, their gut microbiome differed from that of patients without long COVID and those without COVID-19 infection.

These patients had a less diverse and less abundant microbiome; the gut microbiome of patients who did not develop long COVID was similar to those who did not have COVID-19.

Among the species of bacteria found in patients with long COVID, 28 were reduced and 14 were enriched both at hospital admission and at 3 and 6 months after hospital discharge.

At 6 months, patients with long COVID had significantly fewer “friends” F. prausnitzii, and Blautia obeum and a greater abundance of “unfriendly” Ruminococcus gnavus and Bacteroides than people who had not had COVID-19.

On the other hand, the gut microbiome of those who did not develop long COVID only showed 25 bacterial species changes at hospital admission, and this fully recovered after 6 months.

The researchers then looked at the composition of the gut microbiome to see if it was associated with different categories of long COVID symptoms: respiratory; neuropsychiatric (headaches, dizziness, loss of taste and smell, anxiety, lack of concentration, disturbed sleep, bad mood, poor memory, blurred vision); gastrointestinal; skin (hair loss); musculoskeletal; and tired.

Eighty-one bacterial species were associated with different categories of long COVID, and many species were associated with more than two categories of persistent symptoms.

For example, at 6 months, persistent respiratory symptoms were strongly associated with several “unfriendly” opportunistic microbes, including Streptococcus angina, Vestibular streptococcus, Streptococcus gordonii and Clostridium dispricum.

And several species known to boost immunity, including Bifidobacterium pseudocatenulatum, F. prausnitzii, R. inulinivorans and Rose Buria, were exhausted in people with long COVID at 6 months.

Similarly, several species of “unfriendly” bacteria have been linked to poorer performance on the 6-minute walk test in people with long COVID.

Upon admission to hospital, the diversity and richness of gut bacteria in patients who subsequently developed long COVID were significantly lower than in patients who did not, suggesting that microbial profiles Particular bowel movements may indicate increased sensitivity, according to the researchers.

This is an observational study, and as such cannot establish cause. And only a small number of participants were included in the study. But the findings echo those of other research, implicating a disordered gut microbiome in a range of long-term conditions, the researchers point out.

And they conclude: “In summary, the altered composition of the gut microbiome is strongly associated with persistent symptoms in patients with COVID-19 up to 6 months after clearance of the SARS-CoV-2 virus.

“Given the millions of people infected during the ongoing pandemic, our findings are a strong impetus to consider modulating the microbiota to facilitate rapid recovery and reduce the burden of post-acute COVID-19 syndrome.