Biomarkers present in the microbiota of the nose and the upper part of the throat could make it possible to assess the degree of severity of Covid-19 in infected people.
- Unlike people with asymptomatic or moderate form of Covid-19, those who have developed a severe form have an impoverished nasal microbiota.
- The researchers also noted the increased presence of ACE-2 receptors, to which the virus binds, and of pathogenic bacteria likely to increase the risk of a severe form of Covid.
Since the start of the global Covid-19 epidemic a year and a half ago, research has made significant progress in understanding why some patients had mild symptoms of the disease or were asymptomatic, while others developed a severe form. which requires hospitalization.
While certain risk factors increase the risk of a severe form of Covid-19, studies have also shown that severe forms of the disease could result from a genetic or immunological anomaly.
A new study, published in the journal Diagnoses, comes again to bring new answers. According to its authors, from the Department of Medicine of the Medical College of Georgia at the University of Augusta (USA), the microbiota of the nose and the upper part of the throat probably contain biomarkers to assess the degree of disease of a person infected with SARS-CoV-2.
An impoverished nasal microbiota
The researchers analyzed the microbiota of 27 people aged 49 to 78 who were negative for the virus, 30 who were positive but had no symptoms, and 27 who were positive and had moderate symptoms that did not require of hospitalization.
They then found that half of the symptomatic patients did not have a sufficient quantity of microbiota that could be sequenced in their nasopharyngeal cavity. By comparison, the vast majority of positive and asymptomatic patients still had sufficient microbiota.
“We don’t know which came first, the disease or the eradication of the microbiota”, says Dr. Sadanand Fulzele. According to him, the runny nose and sneezing due to the infection could have depleted the microbiota even if at this stage, he does not have sufficient data to support this theory.
Presence of pathogenic bacteria in symptomatic patients
The researchers also found differences in the type of bacteria present in the nasopharynx of people aged 65 and over or with risk factors for hospitalization or a severe form of Covid-19.
SARS-CoV-2 infection occurs when a person coughs, sneezes, or talks, and aerosols carrying the virus travel through the air and enter a person’s nose or mouth. However, the moist lining of the nasopharynx produces mucus, which provides a natural barrier against pathogens. The mucosa also contains a large number of immune cells and ACE-2 receptors, to which the spike protein of the virus binds.
According to the researchers, the altered microbiota of symptomatic patients impacted their immune response to the virus. Thus, symptomatic patients had significantly higher levels of bacterial species like Cutibacterium, a skin bacterium associated with acne but also heart infections and shoulder infections after surgery. High levels of cyanobacteria were also noted. Also called blue-green algae, these bacteria present in contaminated water enter the body through the mucous membranes and can cause pneumonia and liver damage. People who showed symptoms had twice as much of this bacteria as their asymptomatic counterparts.
While the relationship between the nasopharyngeal microbiota and the severity of Covid-19 remains unknown, their study indicates a “strong partnership” between the nasal microbiota, SARS-CoV-2 infection and its severity, write the authors, who specify that their analysis was carried out before the arrival of the variants. But these differences in microbiota will likely apply to variants as well. They have also begun to study them.
.
