Imbalances in gut bacteria linked to 'long COVID' risk: Study

Imbalances in and volume of bacteria found in gut may be associated with risk of 'long COVID’, symptoms of which last for weeks or months beyond initial illness, according to an observational study. research, published in journal Gut, found that variety of bacteria in gut, kwn as microbiome, may influence severity of COVID-19 as well as level of immune system response to infection.

researchers from Chinese University of Hong Kong also found that imbalances in make-up of this microbiome may be implicated in persisting inflammatory symptoms, kwn as 'long COVID'. y ted that COVID-19 is primarily a respiratory illness, but evidence suggests that gut may also play a role.

"In light of reports that a subset of recovered patients with COVID-19 experience persistent symptoms such as fatigue, breathlessness and joint pains, some over 80 days after onset of symptoms, we posit that dysbiotic gut microbiome could contribute to immune-related health problems post-COVID-19," researchers said.

"Bolstering of beneficial gut species depleted in COVID-19 could serve as a vel avenue to mitigate severe disease, underscoring importance of managing patients' gut microbiota during and after COVID-19," y ted.

researchers ted that gut is largest immulogical organ in body and its resident microbes are kwn to influence immune responses. team, refore, wanted to find out if bacteria might also affect immune system response to COVID-19 infection. y obtained blood and stool samples and medical records from 100 hospital inpatients with laboratory-confirmed COVID-19 infection between February and May 2020, and from 78 people without COVID-19 who were taking part in a microbiome study before pandemic.

severity of COVID-19 was classified as mild in absence of x-ray evidence of pneumonia and moderate if pneumonia with fever and respiratory tract symptoms were detected. disease was considered severe if patients found it difficult to brea rmally, and critical if y needed mechanical ventilation or experienced organ failure requiring intensive care.

To characterise gut microbiome, 41 of COVID patients provided multiple stool samples while in hospital, 27 of whom provided serial stool samples up to 30 days after clearance of SARS-CoV-2, virus responsible for COVID-19. Analysis of all 274 stool samples showed that make-up of gut microbiome differed significantly between patients with and without COVID-19, irrespective of wher y h been treated with drugs, including antibiotics.

researchers found that COVID patients h higher numbers of Rumicoccus gnavus, Rumicoccus torques and Bacteroides dorei species than people without infection. y also h far less microbiome species that can influence immune system response, such as Bifidobacterium olescentis, Faecalibacterium prausnitzii and Eubacterium rectale. Fewer numbers of F. prausnitzii and Bifidobacterium bifidum were particularly linked with infection severity after taking into account antibiotic use and patient , according to researchers.

numbers of se bacteria remained low in samples collected up to 30 days after infected patients h cleared virus from ir bodies, y said. COVID-19 infection prompts immune system to produce inflammatory cytokines in response. In some cases, this response can be excessive and le to a 'cytokine storm' which causes widespre tissue dam, and multiorgan failure.

Analysis of blood samples showed that microbial imbalance found in COVID patients was also associated with increased levels of inflammatory cytokines and blood markers of tissue dam. This suggests that gut microbiome might influence immune system response to COVID-19 infection and potentially affect disease severity and outcome, researchers said.

team ted that study is observational, and as such, cant establish cause, ding gut microbiome varies widely among different populations. refore, changes observed in research may t be applicable to or COVID patients elsewhere, y said.