The COVID-19 virus disrupts the normal mixing of gut bacteria, increasing the risk of other infections

A new study has found that infection with the pandemic virus SARS-CoV-2 reduces the number of bacterial species in patients' guts, and less diversity creates space
for dangerous microbes to multiply.

The study builds on the recognition that antibiotics have been widely used in recent decades to fight infections from disease-causing bacteria, killing the species most vulnerable to existing drugs, leaving more antibiotic-resistant species
.
In addition, disturbances in the gut bacterial ratio were previously thought to be linked to
more severe COVID-19.

However, the researchers say that until now, it was not clear whether the coronavirus infection had disrupted the gut microbiome or whether an already weakened gut made the body more vulnerable to the virus
.
New research seems to support the former explanation
more.
The new survey also shows that antibiotic-resistant species can escape into the bloodstream, putting patients at greater risk of
secondary infection.

The survey, led by researchers at NYU's Grossman School of Medicine, involved 96 men and women
hospitalized with COVID-19 in New York City and New Haven, Connecticut, in 2020.
The results showed that the gut microbiota diversity was low in most patients, with a full quarter of patients being dominated
by a single type of bacteria.
At the same time, the number of several known microorganisms, including antibiotic-resistant species, has increased, possibly due
to the widespread use of antibiotics in the early days of the pandemic.

These antibiotic-resistant bacteria found in the gut were also observed migrating into the bloodstream
of 20% of patients.
The study's authors note that further research is needed to reveal why this group is at higher risk of secondary infection, while others remain protected
.

"Our findings suggest that coronavirus infection directly interferes with the healthy balance of gut microbes, further endangering patients in the process," said microbiologist Dr.
Ken Cadwell, senior
co-author of the study.
Cadwell added: "Now that we have identified the source of this bacterial imbalance, doctors can better identify those coronavirus patients who are most likely to develop a secondary bloodstream infection
.
"

Cadwell, a professor in the Department of Microbiology and Medicine at New York University's Langone School of Health, said the new study is the first to show that just coronavirus infection, rather than initially treating the disease with antibiotics, as other experts believe, can disrupt the gut microbiome
.
He added that the study also provides the first evidence that bacteria in the gut can also enter a patient's bloodstream, leading to dangerous infections
.

The report was published online Nov.
1 in the journal Nature Communications
.

In the investigation, the researchers first infected dozens of mice with coronavirus and analyzed the bacterial species composition
in their fecal samples.
This step allowed them to figure out if the coronavirus could directly disrupt the microbiome
independently of hospitalization and treatment.

Next, they collected stool samples and blood tests from COVID-19 patients at NYU Langone Hospital and Yale University Hospital to assess gut microbial composition and the presence of
secondary infections.
If any one type of bacteria makes up the majority of bacteria living in the gut, they are considered the dominant flora
.

"Our findings highlight how closely the gut microbiota and different parts of the human immune system are closely linked," said Jonas Schluter, Ph.
D.
, senior author of the study, an assistant professor in the Department of Microbiology at New York University Langone and a member of
the Institute of Systems Genetics.
"An infection of one can lead to wreaking havoc
on the other.
" Schluter cautions that because patients receive different kinds of treatment, this survey cannot fully explain all the factors
that may contribute to their microbiota disturbance and deterioration.

Schluter said the team's next step is to investigate why certain microbial species are more likely to escape their guts
during COVID-19.
The researchers say they also intend to explore how different microbes interact, which could help with this migration into the bloodstream
.

Gut microbiome dysbiosis in antibiotic-treated COVID-19 patients is associated with microbial translocation and bacteremia