A team of scientists from Brazil recently highlighted the importance of gut microbiota alterations induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in triggering symptoms of post-coronavirus disease 2019 (COVID-19).
The study is recently available on Research Square’s preprint server*.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen to blame for COVID-19, is known to infect a variety of organs beyond the airways. The maximum is infection of the gastrointestinal tract, which causes an abundant alteration in the composition and diversity of the intestinal microbiota. Studies in COVID-19 patients have established an agreement between the alteration of the intestinal microbiota induced by SARS-CoV-2 and the severity of COVID-19.
In the study provided, the scientists investigated the involvement of altered gut microbiota in triggering post-COVID-19 symptoms.
The test was performed on a total of 72 post-COVID patients and 59 healthy people. Fecal samples collected by themselves from the participants were received for the investigation of the composition and diversity of the intestinal microbiota. Samples from COVID-19 patients were collected on average 2 months after SARS-CoV-2 infection. At the time of collection, all fecal samples were negative for SARS-CoV-2.
To determine the functional role of the SARS-CoV-2-modified gut microbiota in triggering post-COVID-19 symptoms, fecal samples taken from participants were transplanted into germ-free mice.
Analysis of fecal samples revealed no significant differences in the composition and diversity of the gut microbiota between COVID-19 patients and healthy individuals. However, estimation of metabolites derived from gut microbiota in the samples revealed reduced levels of acetate and butyrate in COVID-19 patients to those in healthy individuals. These effects imply that SARS-CoV-2 infection alters the metabolism of the gut microbiota.
To investigate the prevalence of antimicrobial-resistant bacteria in fecal samples, it was decided to analyze the circle of relatives of enterobacteria, as these Gram-negative bacteria are known to transmit antimicrobial resistance genes of clinical interest.
The effects revealed a particularly higher point of multidrug-resistant enterobacteria strains on the gut microbiota of COVID-19 patients compared to healthy individuals. A difference in resistance to beta-lactam antibiotics and penicillin has been observed between COVID-19 patients and healthy individuals. In addition, a higher point of Klebsiella and a reduced point of antimicrobial-resistant Escherichia have been observed in the gut microbiota of COVID-19 patients.
It has been estimated that some biomarkers of intestinal integrity and systemic inflammation determine the effect of SARS-CoV-2 infection on overall intestinal homeostasis.
The effects revealed no significant differences in bacterial translocation of the gut between COVID-19 patients and healthy individuals. Similarly, no differences in blood levels of pro-inflammatory mediators were observed between the groups. However, a point of relative decline of cytokine 10 (IL-10) anti-inflammatory interleukin and a higher point of intestinal epithelial damage have been observed in patients with COVID-19.
Overall, these effects suggest that SARS-CoV-2 infection induces epithelial lesions; however, it is related to higher systemic inflammation.
Post-COVID gut microbiota transplantation in mice did not cause significant alterations in the intestinal tract. However, it is known that the lung is the most affected organ. Specifically, a higher point of lung inflammation was observed in mice that gained gut microbiota from COVID-19 patients.
Importantly, no evidence of SARS-CoV-2 RNA was detected in lung tissue, which is consistent with the absence of the virus in fecal samples. Therefore, those effects verify that alteration of the gut microbiota due to a viral infection can directly induce lung infection. inflammation even in the absence of the virus.
In addition, the effects revealed that post-COVID gut microbiota transplantation could make mice more vulnerable to lung infections caused by the antimicrobial-resistant Klebsiella pneumoniae strain.
Regarding changes in the brains of mice, reduced levels of neuroprotective things, brain-derived neurotrophic things (BDNF) and postsynaptic density protein (PSD-95) were observed, and increased expression of the tumor necrosis thing alpha (TNF-alpha) after COVID gut microbiota transplantation.
In addition, a significant effect on post-COVID gut microbiota has been observed in multiple biological pathways vital to overall neurological functions. These adjustments were associated with decreased cognitive functionality in mice.
For further confirmation, a mouse-style beta-coronavirus infection was used in the study. These mice also had cognitive impairment due to a viral infection.
The mice were first pretreated with the probiotic bacterium Bifidobacterium longum five and then subjected to a coronavirus infection. The effects revealed that probiotic modulation of the gut microbiota can prevent cognitive decline related to a viral infection.
The study found that altered gut microbiota caused by SARS-CoV-2 infection may play a role in the progression of long-term symptoms related to COVID-19 even after viral clearance.
Research Square publishes initial clinical reports that are not peer-reviewed and therefore should not be considered as conclusive clinical practices/health-related behaviors or treated as established information.
Written by
Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the strength of science in the 4 corners of the world. He holds a Bachelor of Science (B. Sc. ) and a Master of Science (M. Sc. ) in Biology. and human physiology. After his master’s degree, Sanchari continued his doctoral studies in human physiology. She is the author of more than 10 original study articles, all of which have been published in world-renowned foreign journals.
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Dutta, Sanchari Sinha. (2022, June 23). A establishes a link between post-COVID symptoms and alterations in the intestinal microbiota. Actualités-Médicale. Extracted on July 7, 2022 from https://www. news-medical. net/news/20220623/Study-links-post-COVID -symptoms-with-alterations-in-the-intestine-microbiota. aspx.
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