Impact of COVID-19 on gut–lung microbiota a mini review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) affects the lungs and gastrointestinal tract. However, SARS-CoV-2 chiefly infects lungs through the binding of angiotensin-converting enzyme 2 (ACE2) receptors and type II transmembrane serine protease (TMPRSS2) expressed on the alveolar epithelial cells. Furthermore, the intestinal epithelial cells also express ACE2 receptors. Not only has the SARS-CoV-2 been detected in nasopharyngeal and mid-nasal samples, but also it seems SARS-CoV-2 RNA can be found in the feces of infectious patients. In fact, fecal samples of patients contain RNA of the virus. The intensity of COVID-19 has mainly been associated with aging and comorbidities. Older patients experience a decline in the alteration of the gut microbiome, and COVID-19 has proven to be most fatal in this age group, further emphasizing the potential critical role of gut microbiota in this disease. The lung was formerly believed to be a sterile area free from bacteria. However, the lung microbiome has received more attention due to its recent link to several respiratory illnesses and immunity. In this review article, data from COVID-19 research and gut–lung cross-talk in the prognosis of COVID-19 disease and explored the bidirectional impacts of it on the gut–lung axis microbiome were discussed.