COVID-19 disrupts gut bacteria, may promote antibiotic-resistant secondary infection

COVID-19 may have an impact on some key players in human health and disease prevention—our symbiotic gut bacteria. During the pandemic scientists noted the correlation between reduced diversity in the intestinal flora—fewer species of microbes—and more intense cases of COVID-19. But, per the classic warning about correlation and causation, research published Tuesday in Nature Communications addresses whether the coronaviral chicken came before or after the egg.

Researchers from the NYU Grossman School of Medicine examined both laboratory mice and 96 COVID patients hospitalized in New York and New Haven. Because the mice weren’t being treated in hospitals, the researchers were able to confirm that it was not hospitalization itself that changed their gut flora. They also noted an increase in the number of goblet cells in the guts of infected mice.

In humans, they examined both blood and stool samples. They found that about 20% of the human patients with severe COVID had bacterial communities dominated by only a single species.

Their findings were consistent with the idea that infection with SARS-COV-2 reduced the diversity of the bacterial community and not with the competing hypothesis that a limited bacterial arsenal rendered patients more susceptible to severe COVID. The researchers concluded that it is SARS-COV-2 itself and not the administration of antibiotics that disrupt the microbial community, but they believe that antibiotics may have exacerbated these changes.

The study made another critical finding. In about 20% of patients, antibiotic-resistant bacterial strains had escaped from the gut into the bloodstream, putting them at risk of secondary infection. The research team plans to study this phenomenon further.

The many valuable contributions made by our smallest friends include purifying our wastewater, helping our bodies digest our food and fight of disease.

Read the full text of the study in Nature Communications.

Bernard-Raichon L, Venzon M, Klein J., Axelrad J, Zhang C, Sullivan A, et al. Gut microbiome dysbiosis in antibiotic-treated COVID-19 patients is associated with microbial translocation and bacteremia. Nat Commun 13, 5926 (2022). https://doi.org/10.1038/s41467-022-33395-6