Composition of gut microbiota may be associated with risk of long-term symptoms of SARS-CoV-2 infection

The composition of the gut microbiome may be linked to a person's risk of developing "long-term COVID" many months after initial infection with the SARS-CoV-2 virus that causes COVID-19 infection, according to a study published online in the journal Gut.

The researchers say that microbiome "profiling" may help determine who is most at risk of developing the disease

Post-acute COVID-19 syndrome, known as "long-course coronavirus disease," is characterized by complications and/or persistent symptoms weeks or months after initial infection with COVID-19

This is relatively common, with as many as three-quarters reporting at least one symptom six months after recovering from a COVID-19 infection

Physiological consequences of an excessive immune system response, cellular damage, or critical illness may contribute to the development of prolonged COVID

Evidence is mounting that the gut microbiome -- the trillions of bacteria, fungi and other microbes that inhabit the digestive tract -- is associated with the severity of COVID-19

Given the important role the gut plays in immunity, it is possible that a disturbance of the immune response to COVID-19 infection caused by resident microbes may also affect the recovery process

Therefore, the researchers wanted to find out whether the composition of the gut microbiome might be associated with prolonged COVID, defined as at least one persistent symptom after SARS-CoV-2 has been cleared from the body

They tracked changes in the gut microbiota of 106 patients of varying severity of COVID-19 who were treated at 3 different hospitals between February and August 2020, and 68 untreated patients during the same period.

They did this by analyzing stool samples from participants

The researchers examined the presence of 30 of the most commonly reported prolonged COVID-19 symptoms 3 and 6 months after initial COVID-19 infection

The average age of COVID-19 patients is 48; more than half of them are women

Of these patients, 86 (81%) had prolonged COVID at 3 months and 81 (76.

Six months after initial infection, there were no significant differences between COVID-19 patients and non-COVID-19 patients in terms of age, sex, prevalence of underlying diseases, antibiotic or antiviral drug use, and severity of COVID-19

Of the 68 COVID-19 patients whose stool samples were analyzed at 6 months, 50 were chronically infected with COVID-19

While initial viral load was not associated with prolonged exposure to COVID-19, their gut microbiota differed from those of patients without prolonged exposure to COVID-19 and those without COVID-19

The microbiomes of these patients were low and abundant; the gut microbiomes of patients without prolonged COVID-19 infection were similar to those without COVID-19
.

Among patients with prolonged COVID-19 infection, 28 bacteria were reduced at admission and at 3 and 6 months after discharge, and 14 were enriched
.

At 6 months, patients with prolonged COVID-19 infection had significantly less 'friendly' prausnitzii F.
prausnitzii and Blautia obeum and 'friendly' gninococcus gnavus and Bacteroides vulgatus compared to those without COVID-19 more in quantity
.

On the other hand, the gut microbiota of patients who had not been infected with the new coronavirus for a long time showed changes in only 25 bacterial species upon admission and 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-term COVID symptoms: respiratory; neuropsychiatric (headache, dizziness, loss of taste and smell, anxiety, difficulty concentrating, sleep disruption, Depressed mood, poor memory, blurred vision); stomach; skin (hair loss); musculoskeletal; and fatigue
.

81 bacteria were associated with prolonged COVID in different categories, and many were associated with persistent symptoms in more than two categories
.

For example, at 6 months, persistent respiratory symptoms were strongly associated with several opportunistic "unfriendly" microbes, including Streptococcus angina, Streptococcus vesti, Streptococcus Gordon, and Clostridium bisporus
.

Several known immunity-boosting bacteria, including Bifidobacterium pseudoatenulatum, F.
prausnitzii, R.
inulinivorans and Roseburia hominis, disappeared after 6 months in patients with prolonged COVID-19 infection
.

Likewise, several "unfriendly" bacterial species were associated with poorer 6-minute walk test performance in people with prolonged COVID-19 infections
.

Those with prolonged COVID-19 infection had significantly lower gut bacteria diversity and richness at admission than those without COVID-19, suggesting that specific gut microbial signatures may indicate greater susceptibility, the researchers said
.

This is an observational study, so no cause can be established
.
Only a small number of participants participated in the study
.
But the researchers note that the finding echoes other findings suggesting gut microbiota disturbances under a range of long-term conditions
.

They concluded: "In conclusion, altered gut microbiome composition is strongly associated with persistent symptoms in COVID-19 patients up to 6 months after clearance of SARS-CoV-2 virus
.

"Given that millions of people are infected during the current pandemic, our findings are a powerful driver to consider modulating the microbiome to facilitate timely recovery and reduce the burden of post-COVID-19 post-acute syndrome
.
"