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Fig. 6 | Intensive Care Medicine Experimental

Fig. 6

From: Endotoxemia and circulating bacteriome in severe COVID-19 patients

Fig. 6

Hypothetical pathogenesis of endotoxemia in COVID-19 pneumonia. At early stage, SARS-CoV-2 primarily infects type 2 pneumocytes in the lungs and causes pneumonia which can progress to ARDS and induces susceptibility of secondary bacterial infection by impairing the pulmonary immune response. The virus can enter the bloodstream causing viremia targeting organs with high ACE2 expression including the gut. SARS-CoV-2 infection of enterocytes causes inflammatory response of gastrointestinal tract which results in alteration of the intestinal microenvironment including epithelial hyperpermeability, attenuated local immune system, and dysbiosis of the microbiome. The perturbations of the intestinal microenvironment allow the pathogenic bacteria from the gut lumen to translocate to the bloodstream. Hence, we propose the sources of endotoxin to be majorly from the gut and minorly from the secondary bacterial infection of the lungs. COVID-19, the coronavirus disease 2019; SAR-CoV-2, severe acute respiratory syndrome coronavirus 2; ARDS, acute respiratory distress syndrome; ACE2, angiotensin converting enzyme 2; MOF, multiple organ failure

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