Very severe long COVID linked to differences in lung and mouth microbiomes
People with long COVID have distinct differences in the mix of bacteria that live in their mouths and lungs, according to a study of more than 700 people published in the European Respiratory Journal. The research also shows that these differences in the lung microbiome are linked to respiratory symptoms, as well as the cognitive and digestive problems known to occur in long COVID.
A new study has found that individuals with severe long COVID have distinct differences in their mouth and lung microbiomes compared to those without severe long COVID. The research, published in the European Respiratory Journal, involved over 700 people who were treated for COVID-19 at hospitals across the United Kingdom between February 2020 and March 2021. The participants were divided into four groups based on symptom severity five months after hospital discharge: very severe, severe, moderate, and mild.
The study's lead author, Dr. Daniela Alferes de Lima Headley from the University of Dundee, explained that the microbiome is crucial for maintaining health across the body, making it a potential contributor to long COVID. Prior studies have identified changes in the gut microbiome associated with long COVID, but this research focused on the lung microbiome due to COVID's known respiratory nature.
The researchers used DNA sequencing to analyze saliva and sputum samples from the participants, identifying specific microbes present in their mouths and lungs.
The findings showed that those with very severe long COVID had clear differences in their oral and respiratory microbiomes compared to those with less severe symptoms. These differences were linked to specific symptoms, including reduced lung function, neurocognitive issues like brain fog and memory problems, and gastrointestinal symptoms such as pain, nausea, diarrhea, and loss of appetite.
One notable change associated with long COVID symptoms was an overabundance of bacteria that produce lactic acid, which was also linked to inflammation signs in patients' blood samples.
The study's senior author, Dr. James Chalmers from the University of Dundee, noted that individuals with the most severe symptoms five to six months after COVID infection exhibited significant changes in their mouth and lung microbiomes. Furthermore, these microbiome alterations were associated not only with lung problems but also with cognitive and gut symptoms, suggesting that the lung microbiome could have broader health implications.
However, the researchers acknowledged that it remains unclear whether these microbiome changes preceded the COVID infection or emerged afterward. Additionally, the long-term effects of these changes in patients' microbiomes remain unknown. Dr. Headley emphasized the urgent need to understand the causes of long COVID to develop better treatments, as the microbiome can potentially be modified through antibiotics, probiotics, or other measures.
The researchers hope their findings will spur further research into long COVID and potentially lead to new treatments for this debilitating condition.
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