Long COVID: Gut microbial profile may hold the key

Gut microbiome profile may be associated with a person’s risk of long coronavirus disease (COVID) (also known as post-acute COVID-19 syndrome [PACS]) after their initial infection, researchers from the Chinese University of Hong Kong (CUHK) have revealed.

In the prospective cohort study, 106 COVID-19 patients (mean age, 48.3 years; female, 52.8 percent) and 68 non–COVID-19 individuals (ie, control group) were recruited. In total, 258 faecal samples were collected and analyzed using shotgun metagenomic sequencing. [Gut 2022;71:544-552]

Results of the study showed that 76 percent of patients developed PACS (≥1 persistent symptom 6 months after disease resolution) and 33.0 percent of patients had >3 persistent symptoms at 6 months. The most common symptoms included fatigue (31.3 percent), poor memory (28.3 percent), hair loss (21.7 percent), anxiety (20.8 percent), and difficulty in sleeping (20.8 percent). “There were no significant differences in age, gender, comorbidities, use of antibiotics or antiviral drugs, and severity of COVID-19 in patients with or without PACS at 6 months,” reported the researchers.

Notably, the microbiome of PACS patients significantly differed from that of the control group (p<0.001), whereas patients without PACS showed recovered gut microbiome which was comparable to that of the control group (p=0.470) at 6 months. “Patients with PACS had a less diverse gut microbiome, with significantly fewer favourable bacteria [ie, Faecalibacterium prausnitzii] and a greater abundance of unfavourable bacteria [ie, Ruminococcus gnavus] than people who did not have COVID-19,” the researcher pointed out.

“This is the first study to demonstrate persistent gut dysbiosis at 6 months after recovery from COVID-19 and the link between altered gut microbiota and common lingering symptoms,” remarked Professor Siew-Chien Ng, Associated Director of the Centre for Gut Microbiota Research, CUHK.

A total of 81 bacterial species were found to be associated with different categories of PACS symptoms (ie, respiratory, neuropsychiatric, gastrointestinal), while many species were associated with ≥3 categories of persistent symptoms. Of note, butyrate-producing bacteria, including Bifidobacterium pseudocatenulatum and F. prausnitzii, demonstrated the largest inverse correlations with PACS at 6 months.

In addition, several species of gut bacteria known to boost a person’s immunity were found to be depleted in patients with PACS, including Bifidobacterium adolescentis, Bifidobacterium longum and B. pseudocatelunatum. “Our finding of bacteria taxa and their association with specific post-acute symptoms highlighted that different microbial patterns may contribute to the development of different PACS symptoms, and how the microbiome could potentially serve as a proxy for predicting the development of specific post-acute COVID-19 symptoms,” Ng added.

“Our findings demonstrate that an individual’s gut microbiome profile may affect their susceptibility to long-term complications of COVID-19,” concluded Professor Francis Chan, Director of the Centre for Gut Microbiota Research, CUHK. “Considering that millions of people have been infected during the ongoing pandemic, the findings provide impetus for consideration of microbiota modulation to facilitate timely recovery and reduce the burden of PACS.”