The role of the gut microbiome in respiratory viral infections in general, and in COVID-19 patients in particular, is only beginning to be understood. Previous reports have shown that COVID-19 is accompanied by gastrointestinal symptoms and that persistent adjustments in the microbiome are noticeable in other people with COVID-19 in the long term. In addition, surveys have shown that all COVID-19 patients have differences in gut bacteria populations compared to healthy controls, and that inflamed patients treated with broad-spectrum antibiotics during their hospital stay remain at increased risk of contracting multidrug-resistant secondary infections and dying from septic shock.
Despite those earlier findings, the causal direction of dating between the altered gut microbiome and coronavirus infection remains unclear. Does coronavirus infection result in an altered gut microbiome, or does an already weakened or dysfunctional gut microbiome make the framework more of a virus infection?
A new study, led by researchers at NYU’s Grossman School of Medicine, has now set out to elucidate this relationship. Initially, the researchers tested adjustments in gut microbes discovered in laboratory mice inflamed with SARS-CoV-2 and found that the diversity of other bacterial species in the gut particularly decreased in the early days of infection. Some families of vital bacteria have disappeared from the gut, while other families have proliferated. These findings led the researchers to suspect that the virus would also alter the microbiome in human patients.
They then studied changes in gut microbes in 96 men and women hospitalized with COVID-19 in 2020, in New York and New Haven, Connecticut. The researchers analyzed the microbial communities present in the stool samples collected during each patient’s hospital stay.
The findings, published in the journal Nature Communications, showed that most patients had diversity of microbiomes in the small intestine, as seen in experimental mice, with about a quarter of the patients having a microbiome ruled by a single type of bacteria. At the same time, populations of several microbes known to come with antibiotic-resistant species have increased, most likely due to the widespread use of antibiotics early in the pandemic. Antibiotics kill drug-sensitive species but leave other drug-resistant species in their place.
He also observed that those antibiotic-resistant bacteria discovered in the gut migrated into the bloodstream in 20% of patients. In the blood, they cause life-threatening infections. The study authors note that more studies are needed to figure out why. This organization in the superior threat of secondary infection, while other patients remained protected.
“Our findings suggest that coronavirus infection directly interferes with the healthy balance of microbes in the gut, further endangering patients in the process,” says study co-director and microbiologist Dr. Ken Cadwell. “Now that we’ve discovered the source of this bacterial imbalance, doctors can better identify coronavirus patients who are at risk for a secondary blood infection. “
Under general circumstances, microbes cannot migrate between the gut and the bloodstream unless the intestinal barrier is damaged. In fact, the researchers discovered alterations in intestinal epithelial cells in mice inflamed with SARS-CoV-2, implying that the virus also alters the permeability of the intestinal mucosa. Previous research has also shown that the influenza virus disrupts the gut barrier in mice by damaging the gut microbiota.
In the existing study, patients who were shown to have a microbiome ruled by one type of bacteria suffered migration of this drug-resistant species from the gut into the bloodstream, indicating some involvement of the intestinal barrier. This provoked a secondary infection in those patients who proved fatal, in some cases.
“Our findings highlight how interconnected the gut microbiome and other parts of the body’s immune formula are,” says the study’s lead author, Dr. Jonas Schluter. “An infection in one can lead to primary disruptions in the other. “Schluter cautions that since patients obtained other types of remedies for their disease, the survey also cannot fully explain all the points that would have possibly contributed to the disruption of their microbiome and worsened their disease.
Taken together, the findings of those studies help a situation where gut migration of microorganisms occurs in COVID-19 patients because the virus causes disruption of the overall gut microbiome. This migration leads to blood infections that can be harmful headaches of the disease. According to Schluter, the study team then plans to read about why certain microbial species are more likely to escape from the gut COVID-19. The researchers say they also intend to explore how other microbes interact, possibly contributing to this migration into the bloodstream.
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By Alison Bosman, editor of Earth. com