Coronavirus Disease (COVID-19) Caused by (SARS-CoV-2) Infections: A Real Challenge for Human Gut Microbiota

Abstract

The current COVID-19 pandemic is a great challenge for worldwide researchers in the human microbiota area because the mechanisms and long-term effects of the infection at the GI level are not yet deeply understood. In the current review, scientific literature including original research articles, clinical studies, epidemiological reports, and review-type articles concerning human intestinal infection with SARS-CoV-2 and the possible consequences on the microbiota were reviewed. Moreover, the following aspects pertaining to COVID-19 have also been discussed: transmission, resistance in the human body, the impact of nutritional status in relation to the intestinal microbiota, and the impact of comorbid metabolic disorders such as inflammatory bowel disease (IBS), obesity, and type two diabetes (T2D). The articles investigated show that health, age, and nutritional status are associated with specific communities of bacterial species in the gut, which could influence the clinical course of COVID-19 infection. Fecal microbiota alterations were associated with fecal concentrations of SARS-CoV-2 and COVID-19 severity. Patients suffering from metabolic and gastrointestinal (GI) disorders are thought to be at a moderate-to-high risk of infection with SARS-CoV-2, indicating the direct implication of gut dysbiosis in COVID-19 severity. However, additional efforts are required to identify the initial GI symptoms of COVID-19 for possible early intervention.

Keywords: COVID-19; coronavirus; dysbiosis; gut microbiota; metabolic disorders; nutrition; severe acute respiratory syndrome coronavirus 2.

Figure 1

The distribution of number of research papers published on PubMed and Web of Science over the past two decades. The results plotted in the graph were obtained by searching the cited databases for articles published over the past two decades. The search keywords were as follows: [(COVID) OR (coronavirus) OR (COVID-19) OR (2019-nCoV) OR (SARS-CoV-2)] AND [(gut) OR (microbiota) OR (diabetes) OR (obesity)].

Figure 2

Interspecies severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (causal organism for the coronavirus disease (COVID-19)) transmission routes, and the associated respiratory and gastrointestinal symptoms. SARS-CoV-2 has extreme transmissibility, and it successfully jumps from animal to human hosts, causing major outbreaks of COVID-19, an emerging zoonotic disease. It causes both respiratory and gastrointestinal symptoms (image created using BioRender application https://app.biorender.com).

Figure 3

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cell infection mechanism. SARS-CoV-2 is surrounded by spiky glycoproteins, also defined as peplomers. The glycoproteins consist of two functional subunits, S1 and S2. The S1 subunit is responsible for host cell receptor binding and stabilization of the viral entity, while the S2 subunit facilitates the fusion of the viral and cellular membranes. After invading the human body, SARS-CoV-2 binds to angiotensin converting enzyme 2 (ACE2), which is found on the exterior surfaces of multiple types of cells. ACE2 - angiotensin converting enzyme 2 (image created using BioRender application https://app.biorender.com).

Figure 4

Intestinal infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leads to dysbiosis, especially due to the occurrence of diarrhea. Enterocytes are damaged and show a high level of overexpression of enzymes which lead to rapid cell degradation (image created using BioRender application https://app.biorender.com).