COVID-19 virus increases risk for other infections by disrupting normal mix of gut bacteria

Infection with the pandemic virus, SARS-CoV-2, can reduce the number of bacterial species in a patient’s gut, with the lesser diversity creating space for dangerous microbes to thrive, a new study finds.

The study builds on the realization that widespread use of antibiotics to fight infections with disease-causing bacteria in recent decades, by killing off species most vulnerable to available drugs, has left in place more species that are resistant to antibiotics. In addition, disruptions in gut bacterial ratios have previously been linked to more severe COVID-19.

However, researchers say, it has remained unclear until now which came first, the coronavirus infection disrupting the gut microbiome or an already weakened gut making the body more vulnerable to the virus. The new study appears to favor the former explanation. The new investigation also revealed that antibiotic-resistant species can escape into the bloodstream, putting patients at greater risk for life-threatening secondary infections.

Led by researchers at NYU Grossman School of Medicine, the investigation involved 96 men and women hospitalized with COVID-19 in 2020 in New York City and in New Haven, Conn. Results showed that the majority of patients had low gut microbiome diversity, with a full quarter dominated by a single type of bacteria. At the same time, populations of several microbes known to include antibiotic-resistant species increased, possible due to widespread antibiotic use early in the pandemic.

These antibiotic-resistant bacteria found in the gut were also observed to have migrated into the bloodstream in 20% of patients. The study authors note that further research is needed to uncover why this group was at higher risk for a secondary infection while others 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-senior author and microbiologist Ken Cadwell, PhD. “Now that we have uncovered the source of this bacterial imbalance, physicians can better identify those coronavirus patients most at risk of a secondary bloodstream infection,” adds Cadwell.

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