Background To investigate the potential beneficial effect of fecal microbiota transplantation (FMT) on gastrointestinal symptoms, gut dysbiosis and immune status in discharged COVID-19 patients. Case presentation A total of 11 COVID-19 patients were recruited in April, 2020, about one month on average after they were discharged from the hospital. All subjects received FMT for 4 consecutive days by oral capsule administrations with 10 capsules for each day. In total, 5 out of 11 patients reported to be suffered from gastrointestinal symptoms, which were improved after FMT. After FMT, alterations of B cells were observed, which was characterized as decreased naive B cell (P = 0.012) and increased memory B cells (P = 0.001) and non-switched B cells (P = 0.012).The microbial community richness indicated by operational taxonomic units number, observed species and Chao1 estimator was marginally increased after FMT. Gut microbiome composition of discharged COVID-19 patients differed from that of the general population at both phylum and genera level, which was characterized with a lower proportion of Firmicutes (41.0%) and Actinobacteria (4.0%), higher proportion of Bacteroidetes (42.9%) and Proteobacteria (9.2%). FMT can partially restore the gut dysbiosis by increasing the relative abundance of Actinobacteria (15.0%) and reducing Proteobacteria (2.8%) at the phylum level. At the genera level, Bifidobacterium and Faecalibacterium had significantly increased after FMT. Conclusions After FMT, altered peripheral lymphocyte subset, restored gut microbiota and alleviated gastrointestinal disorders were observe, suggesting that FMT may serve as a potential therapeutic and rehabilitative intervention for the COVID-19.

Coronavirus disease 2019 (COVID-19), which was outbreak in December 2019 Wuhan, China, has spread to more than 100 countries. In addition to respiratory symptoms, COVID-19 can also cause some digestive symptoms such as nausea and diarrhea. As a variety of respiratory diseases which are associated with a dysbiosis in both airway microbiota and the intestinal microbiota, COVID-19 may cause digestive symptoms through a constant cross-talk between the system which is known as the Gut-Lung Axis. Additionally, lymphopenia and hypercytokinemia were also common in COVID-19 patients which suggest that COVID-19 could compromise the immune system. Given the fact that gut microbiota not only could maintain immune homeostasis and immune responses at local mucosal surfaces, but also has distal protective effects and protect against respiratory virus. FMT is an effective way to enhance immunity and would be a potential therapy for individuals with viral infection. However, currently no direct clinical evidence proved that modulation of gut microbiota has the therapeutic role in treatment of COVID-19, from the perspective of microbiota and immunity after viral infection, we speculate that targeting gut microbiota might be a new therapeutic option or at least adjuvant therapeutic choice. In this Personal View, we describe the five aspects: COVID-19 and compromised immunity system, Microbiota, immune system and viral infection, FMT, immunity and virus infection, potential application of FMT in the treatment of COVID-19.

Background: Gastrointestinal manifestations and gut dysbiosis are prevalent after SARS-CoV2 infection.With the continuously increasing number of infected cases, more attention should be paid to this particular population in post-infection recovery.cWe aimed to investigate the potential beneficial effect of FMT on gastrointestinal symptoms, gut dysbiosis and immune status in discharged COVID-19 patients. Results: Gastrointestinal and psychological disorder (45.5%) were observed in COVID-19 patients during post-infection recovery, improvement of which were observed after FMT. Most of the lab results including blood routine and blood biochemistry, within the normal range. The general distribution of 69 different types of lymphocytes differed between before and after FMT. FMT exert significant effect on B cells which was characterized as decreased naive B cell ( P =0.012) and increased memory B cells ( P = 0.001) and non-switched B cells ( P = 0.012).The microbial community richness indicated by OTUs number, observed species and Chao1 estimators was marginally increased after FMT, whereas the community diversity estimated by the Shannon and Simpson index showed no significant changes after FMT. Gut microbiome composition of discharged COVID-19 patients differed from that of the general population at both phylum and genera level, which was characterized with a lower proportion of Firmicutes (41.0%) and Actinobacteria (4.0%), higher proportion of Bacteroidetes (42.9%) and Proteobacteriato (9.2%). FMT can partially restore the gutdysbiosis by increasing the relative abundance of Actinobacteria (15.0%) and reducing Proteobacteriato (2.8%) at the phylum level. At the genera level, Bifidobacterium and Faecalibacterium , which were dominant genera in the human gut microbiota and were beneficial for human health, had significantly increased after FMT. Conclusions: Gastrointestinal and gut dysbiosis were observed in COVID-19 patients during post-infection recovery. FMT can improve the immune functionality, restore the gut microbiota, alleviate gastrointestinal disorders, and may serve as a potential therapeutic and rehabilitative intervention for the COVID-19.