Covid-19: gut microbiota in the dock
The gut microbiota may influence the severity of Covid-19, with a gut imbalance thought to persist even after the virus is eliminated. These results nonetheless remain preliminary and require confirmation.
From the outset of the Covid-19 pandemic, some patients have reported digestive symptoms, particularly diarrhea. This has prompted researchers to study patients’ gut microbiota to see whether the bacteria, fungi and viruses living in the gut impact our immune defenses. The results of a new study in Hong Kong seem to validate the link between the gut microbiota and the disease. However, further studies will be required to confirm these findings, which were obtained in the heat of the action in early 2020 and suffer from several methodological flaws.
Dysbiosis in Covid-19 patients
The study focused on relatively young Covid-19 patients (average age: 36.4 years) mostly with mild forms of the disease (47 mild cases, 45 moderate cases, 5 severe cases and 3 critical cases)1. What does it reveal? Firstly, these patients presented an imbalance of the gut flora (dysbiosis) that was not present in healthy patients. It was depleted in certain bacteria beneficial to the regulation of immunity. Second, the more severe the case and the higher the levels of inflammation markers in the patient’s blood, the greater the dysbiosis. It therefore seems as if the gut microbiota plays a role in regulating the disease by modulating inflammatory processes. However, this mechanism remains to be confirmed. The study does not clarify whether the dysbiosis is the cause or consequence of the severity of the symptoms observed.
Dysbiosis persists after virus clearance
Another observation of the researchers was that this gut dysbiosis, which seems to increase with antibiotic treatments, persists even after the virus has been eliminated from the body. This led to the tentative hypothesis that the gut flora imbalance may contribute to the persistent symptoms observed in some patients.
1 34% of patients were taking antibiotics and 31% had comorbidities (hypertension, hyperlipidemia, allergies, etc.)
Yeoh YK, Zuo T, Lui GC, et al. Gut microbiota composition reflects disease severity and dysfunctional immune responses in patients with COVID-19. Gut. 2021 Jan 11:gutjnl-2020-323020. doi: 10.1136/gutjnl-2020-323020.