Background & Aims Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects gastrointestinal tissues, little is known about the roles of gut commensal microbes in susceptibility to and severity of infection. We investigated changes in fecal microbiomes of patients with SARS-CoV-2 infection during hospitalization and associations with severity and fecal shedding of virus. Methods We performed shotgun metagenomic sequencing analyses of fecal samples from 15 patients with Coronavirus Disease 2019 (COVID-19) in Hong Kong, from February 5 through March 17, 2020. Fecal samples were collected 2 or 3 times per week from time of hospitalization until discharge; disease was categorized as mild (no radiographic evidence of pneumonia), moderate (pneumonia was present), severe (respiratory rate ≥30/min, or oxygen saturation ≤93% when breathing ambient air), or critical (respiratory failure requiring mechanical ventilation, shock, or organ failure requiring intensive care). We compared microbiome data with those from 6 subjects with community-acquired pneumonia and 15 healthy individuals (controls). We assessed gut microbiome profiles in association with disease severity and changes in fecal shedding of SARS-CoV-2. Results Patients with COVID-19 had significant alterations in fecal microbiomes compared with controls, characterized by enrichment of opportunistic pathogens and depletion of beneficial commensals, at time of hospitalization and at all timepoints during hospitalization. Depleted symbionts and gut dysbiosis persisted even after clearance of SARS-CoV-2 (determined from throat swabs) and resolution of respiratory symptoms. The baseline abundance of Coprobacillus, Clostridium ramosum, and Clostridium hathewayi correlated with COVID-19 severity; there was an inverse correlation between abundance of Faecalibacterium prausnitzii (an anti-inflammatory bacterium) and disease severity. Over the course of hospitalization, Bacteroides dorei, Bacteroides thetaiotaomicron, Bacteroides massiliensis, and Bacteroides ovatus, which downregulate expression of angiotensin-converting enzyme 2 (ACE2) in murine gut, correlated inversely with SARS-CoV-2 load in fecal samples from patients. Conclusions In a pilot study of 15 patients with COVID-19, we found persistent alterations in the fecal microbiome during the time of hospitalization, compared with controls. Fecal microbiota alterations were associated with fecal levels of SARS-CoV-2 and COVID-19 severity. Strategies to alter the intestinal microbiota might reduce disease severity.

Objective The gut microbiota has been suggested to play a role in autism spectrum disorder (ASD). We postulate that children with ASD harbour an altered developmental profile of the gut microbiota distinct from that of typically developing (TD) children. Here, we aimed to characterise compositional and functional alterations in gut microbiome in association with age in children with ASD and to identify novel faecal bacterial markers for predicting ASD. Design We performed deep metagenomic sequencing in faecal samples of 146 Chinese children (72 ASD and 74 TD children). We compared gut microbial composition and functions between children with ASD and TD children. Candidate bacteria markers were identified and validated by metagenomic analysis. Gut microbiota development in relation to chronological age was assessed using random forest model. Results ASD and chronological age had the most significant and largest impacts on children’s faecal microbiome while diet showed no correlation. Children with ASD had significant alterations in faecal microbiome composition compared with TD children characterised by increased bacterial richness (p=0.021) and altered microbiome composition (p<0.05). Five bacterial species were identified to distinguish gut microbes in ASD and TD children, with areas under the receiver operating curve (AUC) of 82.6% and 76.2% in the discovery cohort and validation cohort, respectively. Multiple neurotransmitter biosynthesis related pathways in the gut microbiome were depleted in children with ASD compared with TD children (p<0.05). Developing dynamics of growth-associated gut bacteria (age-discriminatory species) seen in TD children were lost in children with ASD across the early-life age spectrum. Conclusions Gut microbiome in Chinese children with ASD was altered in composition, ecological network and functionality compared with TD children. We identified novel bacterial markers for prediction of ASD and demonstrated persistent underdevelopment of the gut microbiota in children with ASD which lagged behind their respective age-matched peers.

Background & Aims Beyond bacteria, the human gastrointestinal tract is host to a vast diversity of fungi, collectively known as the gut mycobiome. Little is known of the impact of geography, ethnicity, and urbanization on the gut mycobiome at a large population level. We aim to delineate the variation of human gut mycobiome and its association with host factors, environmental factors, and diets. Methods Using shotgun metagenomic sequencing, we profiled and compared the fecal mycobiome of 942 healthy individuals across different geographic regions in China (Hong Kong and Yunnan), spanning 6 ethnicities: Han, Zang, Bai, Hani, Dai, and Miao (including both urban and rural residents of each ethnicity). In parallel to fecal sampling, we collected participant metadata (environmental exposure, bowel habits, anthropometrics, and medication), diet, and clinical blood measurement results (a total of 118 variables) and investigated their impact on the gut mycobiome variation in humans. Results The human gut mycobiome was highly variable across populations. Urbanization-related factors had the strongest impact on gut mycobiome variation, followed by geography, dietary habit, and ethnicity. The Hong Kong population (highly urbanized) had a significantly lower fungal richness compared with Yunnan population. Saccharomyces cerevisiae was highly enriched in urban compared with rural populations and showed significant inverse correlations with liver pathology–associated blood parameters, including aspartate transaminase, alanine transaminase, gamma-glutamyltransferase, and direct bilirubin. Candida dubliniensis, which was decreased in urban relative to rural populations, showed correlations with host metabolism-related parameters in blood, including a positive correlation with fasting high-density lipoprotein cholesterol levels and a negative correlation with fasting glucose levels. The fungal-blood parameter correlations were highly geography- and ethnicity-specific. Food choices had differential influences on gut mycobiome and bacterial microbiome, where taxa from the same genus tended to be coregulated by food and thereby cobloom. Ethnicity-specific fungal signatures were associated with distinct habitual foods in each ethnic group. Conclusions Our data highlight, for the first time to our knowledge, that geography, urbanization, ethnicity, and habitual diet play an important role in shaping the gut mycobiome composition. Gut fungal configurations in combination with population characteristics (such as residing region, ethnicity, diet, lifestyle) influence host metabolism and health.

Background: Coronavirus disease 2019 (COVID-19) caused by the enveloped RNA virus SARS-CoV-2 primarily affects the respiratory and gastrointestinal tracts. SARS-CoV-2 was isolated from fecal samples, and active viral replication was reported in human intestinal cells. The human gut also harbors an enormous amount of resident viruses (collectively known as the virome) that play a role in regulating host immunity and disease pathophysiology. Understanding gut virome perturbation that underlies SARS-CoV-2 infection and severity is an unmet need. Methods: We enrolled 98 COVID-19 patients with varying disease severity (3 asymptomatic, 53 mild, 34 moderate, 5 severe, 3 critical) and 78 non-COVID-19 controls matched for gender and co-morbidities. All subjects had fecal specimens sampled at inclusion. Blood specimens were collected for COVID-19 patients at admission to test for inflammatory markers and white cell counts. Among COVID-19 cases, 37 (38%) patients had serial fecal samples collected 2 to 3 times per week from time of hospitalization until after discharge. Using shotgun metagenomics sequencing, we sequenced and profiled the fecal RNA and DNA virome. We investigated alterations and longitudinal dynamics of the gut virome in association with disease severity and blood parameters. Results: Patients with COVID-19 showed underrepresentation of Pepper mild mottle virus (RNA virus) and multiple bacteriophage lineages (DNA viruses) and enrichment of environment-derived eukaryotic DNA viruses in fecal samples, compared to non-COVID-19 subjects. Such gut virome alterations persisted up to 30 days after disease resolution. Fecal virome in SARS-CoV-2 infection harbored more stress-, inflammation-, and virulence-associated gene encoding capacities including those pertaining to bacteriophage integration, DNA repair, and metabolism and virulence associated with their bacterial host. Baseline fecal abundance of 10 virus species (1 RNA virus, pepper chlorotic spot virus, and 9 DNA virus species) inversely correlated with disease COVID-19 severity. These viruses inversely correlated with blood levels of pro-inflammatory proteins, white cells, and neutrophils. Among the 10 COVID-19 severity-associated DNA virus species, 4 showed inverse correlation with age; 5 showed persistent lower abundance both during disease course and after disease resolution relative to non-COVID-19 subjects. Conclusions: Both enteric RNA and DNA virome in COVID-19 patients were different from non-COVID-19 subjects, which persisted after disease resolution of COVID-19. Gut virome may calibrate host immunity and regulate severity to SARS-CoV-2 infection. Our observation that gut viruses inversely correlated with both severity of COVID-19 and host age may partly explain that older subjects are prone to severe and worse COVID-19 outcomes. Altogether, our data highlight the importance of human gut virome in severity and potentially therapeutics of COVID-19.