Why do some people develop severe COVID symptoms from the novel coronavirus?

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The nasal microbiota contains clues about who will develop symptoms of COVID from the novel coronavirus.

The microbiota of the nose and upper throat probably contains biomarkers to assess the disease of an individual infected with SARS-CoV-2 can obtain and to develop new treatment strategies to improve their results, according to the researchers.

This nasopharyngeal microbiota is generally considered a first-line protection against viruses, bacteria and other pathogens that enter these natural passageways, says Dr. Sadanand Fulzele, a geriatric researcher in the Department of Medicine at the Medical College of Georgia in the United States. ‘University of Augusta.

Distinct patterns emerged when the researchers examined 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 with moderate symptoms not having any symptoms. no need for hospitalization, they report in the newspaper Diagnostic.

“Millions of people are infected and relatively few of them become symptomatic. This could be one of the reasons, ”says Dr. Ravindra Kolhe, director of the Georgia Esoteric and Molecular Laboratory at MCG, or GEM Lab. who performed more than 100,000 COVID tests.

Sadanand Fulzele and Ravindra Kolhe

Dr Sadanand Fulzele (left) and Dr Ravindra Kolhe. Credit: Michael Holahan, Augusta University

The most significant changes occurred in those who were symptomatic, including about half of the patients who did not have enough microbiota to even sequence, says corresponding author Fulzele.

They were surprised to find these “low readings” of bacteria in the nasopharyngeal cavity of symptomatic individuals compared to only two and four individuals in the negative and positive groups without symptoms, respectively. The vast majority of positive individuals without symptoms still had sufficient microbiota, notes first author Kolhe.

“We don’t know what happened first, the disease or the erosion of the microbiota,” says Fulzele. The runny nose and sneezing could explain the loss, an already significantly lower number of bacterial inhabitants could have increased individuals’ risk of developing these kinds of symptoms, or the virus may have changed the landscape, says Fulzele, who suspects that it is the latter.

Based on the experience of the microbiota in the gastrointestinal tract, Kolhe believes that the different content and size of the microbiota is another good bet and they both would like a definitive answer. “We don’t have enough data at the moment,” says Kolhe.

They also found differences in the type of bacteria, although the researchers note that the function of some of the bacteria they found is not well understood.

As the name of the virus and almost two years of experience with it indicate, a major method of transmission of Severe Acute Respiratory Syndrome Coronavirus 2, or SARS-Cov-2, is when a person coughs, sneezes. or even speaks, and droplets called aerosols carrying the virus travel through the air and into another person’s nose or mouth.

People aged 65 and over and / or with underlying health conditions like hypertension and diabetes are considered to be at increased risk of hospitalization and death from the infection. older individuals.

The moist, mucus-producing lining of this area works as a natural barrier against invaders and there is also a significant complement of immune cells present, Fulzele says, and their response to respiratory viruses is key.

The area is also teeming with ACE-2 receptors, which the spiny virus binds to, and Kolhe says it’s a major landing point for this virus.

Their new findings indicate that the altered microbiota in symptomatic patients impacted their immune response to the virus, according to Kolhe and Fulzele.

Symptomatic individuals had significantly higher levels of two bacterial species, including Cutibacterium, commonly found on the skin and associated with acne but also heart infections and shoulder infections following surgery. Conversely, there was a significantly lower presence of a handful of other poorly studied bacteria.

The microbiota from both infected groups, symptomatic and asymptomatic, exhibited high levels of bacteria like cyanobacteria, also known as blue-green algae, which can be found in contaminated water but is a habitual inhabitant of the microbiome in humans. man who seems to have a regulatory role. the immune response. These bacteria usually enter the body through mucous surfaces, such as those on the nose, and are known to cause pneumonia and liver damage. Those who were symptomatic had twice as much of this bacteria as their asymptomatic counterparts.

Fulzele notes that between the asymptomatic and symptomatic, there was no significant change in microbiota diversity – just these big differences in volume – but they saw a lot of individual bacteria go up and down in number.

For example, their graph of the number of another hydrophilic bacterium, Amylibacter, looked like stairs as it went from negative to positive with symptoms, while there was a downward trend for a handful. other bacteria.

While the relationship between the nasopharyngeal microbiota and the severity of COVID-19[female[feminine remains unknown, their study indicates a “strong association” between nasal microbiota, SARS-CoV-2 infection and severity, they write.

Their analysis was done before the current viral variants started to surface, but the researchers say the differences in the microbiota will likely hold true for these as well, and they have already started this analysis.

Larger studies are needed to make sure the clear patterns they found hold up, the researchers say. They are preparing a grant application that will allow for a larger study and are looking for other test sites that wish to be partners. Using the same nasopharyngeal swab used for many COVID tests would allow a microbiota scan to be performed at the same time as the tests, they say.

They note the stark contrast that has emerged over nearly two years of experience with the virus, with the majority of those infected being asymptomatic or showing mild symptoms as they would with a cold, while others contract pneumonia. viral disease, require hospitalization and die.

A handful of recent studies have now been published suggesting that the bacterial makeup of the nasal canal may have a “drastic” influence on the development of respiratory infections and the severity of symptoms, they write. Some studies have indicated that the nasal microbiota can influence viral load, immune response, and symptoms of a rhinovirus infection, which is responsible for 10-40% of colds.

A myriad of other conditions like inflammatory bowel syndrome, peptic ulcers and viral diseases have been linked to significant changes in the microbiota of the gut, nasal cavity and oral cavity, they write.

The diversity of bacteria in the microbiota is generally a good thing, and it’s something that naturally decreases with age, Fulzele says, and can also be altered by habits like smoking and improved by those like a diverse diet.

Reference: “Altered Nasopharyngeal Microbiota Profile in Elderly Patients with COVID-19” by Ravindra Kolhe, Nikhil Shri Sahajpal, Sagar Vyavahare, Akhilesh S. Dhanani, Satish Adusumilli, Sudha Ananth, Ashis K. Mondal, G. Taylor Patterson , Sandeep Kumar, Amyn M. Rojiani, Carlos M. Isales and Sadanand Fulzele, September 5, 2021, Diagnostic.
DOI: 10.3390 / diagnostics11091622

The work was supported in part by the National Institutes of Health.


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