Significant Gut Microbiota Differences Found in COVID-19 Patients, Healthy Individuals

SeyedAhmad SeyedAlinaghi

SARS-CoV-2 infections are known to cause disruptions in the gut microbiota.

A team, led by SeyedAhmad SeyedAlinaghi, Iranian Research Center for HIV/AIDS, Iranian Institute for Reduction of High Risk Behaviors, Tehran University of Medical Sciences, systematically reviewed the effects of gut microbiota on SARS-CoV-2 infections and its severity and the impact the infection could have in turn on the gut microbiota.

Patients with COVID-19 infections often present with alterations in the gut microbiota, as well as gastrointestinal symptoms including anorexia, diarrhea, nausea or vomiting, and abdominal pain.

“Few studies discovered dysbiosis and a rise in GI opportunistic microorganisms in patients infected with SARS-CoV-2 that suggested a possible link between the gut-lung axis and SARS-CoV-2,” the author wrote. “An obvious association exists between the overall health of the gut microbiome and the progression of COVID-19. Additionally, the altered gut microbiota has been shown to persist in patients even after several days up to 6 months after clearance of COVID-19.”

While the gut and upper respiratory tract microbiota hosts a dynamic and complex population of microorganisms with known strong interactions with host immune system homeostasis, the knowledge of the association between the gut microbiota and SARS-CoV-2 is still limited.

In the study, the investigators reviewed various databased and identified 63 studies that adhered to the PRISMA checklist and Newcastle−Ottawa Scale Bias Assessment tool of the 829 studies originally assessed.

Incomplete studies, non-original studies, nonhuman studies, and case reports were excluded.

Eligible studies were then evaluated for the relationship between the gut microbiota and COVID-19, which either effect being considered.

The majority of studies were conducted in 2021 (88.8%) and 2020 (9.52%). The investigators used 11 articles based in the US and 25 articles based in China. The remaining 6 articles were based in Italy, Russia (n = 3), and other countries.

The majority of studies examined showed SARS-CoV-2 infections cause microbiome dysbiosis, while at least 1 show an increase in opportunistic pathogens and a decrease in beneficial bacteria.

The investigators found the composition of microbiota could also be linked to the severity of COVID-19.

In the final analysis, the investigators found moderate to severe cases of COVID-19 resulted in gut and lung microbiota that differed from healthy individuals. The investigators also found the severity and viral load of COVID-19 disease probably would be influenced by the gut and lung microbiota’s composition.

Some studies also showed the abundance and diversity of upper respiratory tract microbiota was not different in patients with mild COVID-19 and healthy individuals.

Specifically, 2 studies showed the beneficial effects of Bifidobacterium in decreasing mortality rates and hospital admission duration of moderate/severe COVID-19 patients, increasing blood antibody levels, and lowering inflammatory cytokines, while 1 study showed the use of probiotics was associated with a shorter duration of COVID-19 illness and hospitalization and improved the conditions of COVID-19 patients.

“Our study concludes that there was a significant difference in the composition of the URT, and gut microbiota in COVID-19 patients compared to the general healthy individuals, with an increase in opportunistic pathogens,” the authors wrote. “Further, research is needed to investigate the probable bidirectional association of COVID-19 and human microbiome.”

The study, “Gut microbiota and COVID-19: A systematic review,” was published online in Health Science Reports.