Connie L. Brenstuhl
This literature review is aimed at assessing and summarizing relationships between the state of the microbiome and susceptibility to respiratory tract infections including COVID-19. It explores using probiotic therapy for patients infected with COVID-19, to improve outcomes, lessen the severity of symptoms, or prevent infection entirely. The coronavirus COVID-19 is known scientifically as severe acute respiratory syndrome coronavirus-2. The virus's binding sites for cell entry, the angiotensin-converting enzyme-2, are found in high concentrations in both respiratory and gut tissues. Probiotics may inhibit angiotensin-converting enzyme-2 receptor activity, thereby blocking viral entry into the cell. COVID-19 infection with alpha and delta variants has manifested clinically both in severe respiratory and gastrointestinal symptoms. The impact on the host’s microbiome is significant and it has been shown that imbalanced intestinal microbiota can negatively affect respiratory function in an immune response known as the gut-lung axis.
The main nutritional outcomes for most people surviving a critical viral-induced respiratory illness include suboptimal protein and calorie intake, hypermetabolism, and rapid muscle wasting. A dysbiosis occurs in the microbiome, allowing opportunistic pathogens to thrive, while beneficial commensals are depleted. The current understanding of the potential mechanisms of probiotic therapy administration, strain specificity, and the effectiveness of these bacteria in preventing and treating COVID-19 infections is summarized. The known antiviral properties of probiotics and their metabolites suggest they may be used as adjunctive therapy in the fight against many respiratory infections.
Addressing dysbiosis with probiotics has shown it is possible to restore a stable intestinal microbiome. The potential role probiotics play in preventing or limiting the intensity and duration of upper respiratory tract infections needs further and wider exploration. Manipulating the gut-lung axis through probiotic therapy suggests great effectiveness in protection against the susceptibility to a wide range of respiratory tract infections.