The Long Hauler Microbiome

The long hauler microbiome is not something mainstream media is addressing. Long haulers are those people with persisting symptoms after infection with COVID-19, even after tested clearance of the virus. Other names for long hauler syndrome are post-COVID syndrome, long COVID, or long-term COVID. Research shows that a long hauler microbiome may play a role in their lingering symptoms.

What Is a Long Hauler Microbiome?

Up to 75% of COVID-19 patients are said to have at least one symptom at 6 months post-recovery. Several studies have shown that these people have dysbiosis (altered gut microbiome) but with certain patterns suggested. These patterns distinguish the long-hauler microbiome from general dysbiosis.

In the journal Gut, a study published at the end of January provided new insights into the relationship between a dysfunctional gut microbiome and the potential for long-term consequences from COVID-19. The study also suggested that microbiome analysis may be a useful tool to determine risk for post-acute COVID-19 syndrome (PACS), defined as having one or more persistent symptoms 4 weeks after clearance of the virus.

This study did not show cause-and-effect, but rather explored the relationship between dysbiosis in the long hauler microbiome and PACS. It should be noted that this is not the first study to show dysbiosis in hospitalized patients with COVID-19, however it investigated bacterial relationships causing dysbiosis and considered a longer time period than previous studies.

In previous studies, a small-sample study of 15 patients published in the journal Gut in 2020 showed a decrease in commensal bacteria and an increase in opportunistic pathogens in hospitalized COVID-19 patients. These alterations were associated with stool levels of COVID-19 virus and severity.

Another study investigating viral stool analysis of the same group of patients showed that even when respiratory symptoms of the virus passed, and without obvious gastrointestinal symptoms, there was still background gastrointestinal infection present. 

Another study published in 2021 with 100 COVID-19 hospitalized patients considered blood, stool, and patient records. Stool samples from 27 of those patients collected up to 30 days post-clearance of the virus showed that gut microbiome composition was significantly altered in patients with COVID-19 compared with individuals without the virus. The dysbiosis was associated with disease severity along with elevated markers of inflammatory molecules in blood. At the time, the researchers commented that continuing gut dysbiosis in the long hauler microbiome after viral clearance could contribute to persistent symptoms.

The Latest Research on the Long Hauler Microbiome

In this 2022 study, researchers followed 106 patients with various levels of COVID-19 severity, from asymptomatic to critical, from hospital admission to 6 months later, and 68 non-COVID-19 controls. Stool analysis was performed on 68 of those patients.

At 6 months, 76% of patients had PACS with the most common symptoms of fatigue, poor memory, and hair loss. Anxiety and difficulty sleeping were the two next common symptoms. Thirty-five percent of patients had more than 3 persistent symptoms.

Among 68 patients with COVID-19 who had stool analysis performed at 6 months, researchers found that a specific long hauler microbiome dysbiosis pattern at admission to the hospital was associated with the occurrence of PACS, and that at 6 months post-COVID, that pattern persisted. To the contrary, patients without PACS showed recovered gut microbiota communities at 6 months, which were similar to the non-COVID-19 controls. Interestingly, the researchers found no significant correlations between respiratory and stool viral loads and PACS development.

Specifically, the gut long hauler microbiome of patients with PACS contained higher levels of Ruminococcus gnavus and Bacteroides vulgatus. These are both common gut colonizers, but are known to be associated with inflammatory conditions when present in disproportionately high numbers. Lower levels of Faecalibacterium prausnitzii, a butyrate-producing bacteria, and Bifidobacterium pseudocatenulatum, a normal gut beneficial species, were found.

In fact, the worse the PACS, the lower the levels of these two beneficial species. Interestingly, low levels of the probiotic species Bifodobacterium longum at admission was correlated with PACS at 6 months. Combined, these results showed that gut dysbiosis played a role in the severity of COVID-19 infection.

Additionally, persistent respiratory symptoms correlated with opportunistic gut pathogens in the long-hauler microbiome, many in the Streptococcus genus. Neuropsychiatric symptoms (headache, dizziness, loss of taste, loss of smell, anxiety, difficulty in concentration, difficulty in sleeping, sadness, poor memory, blurred vision) and fatigue were correlated with gut pathogens that are commonly acquired in a healthcare setting, such as Clostridium innocuum and Actinomyces naeslundii . Both of those correlations showed dysbiosis in the long hauler microbiome.

The significance of this most recent study is that it showed persistent gut dysbiosis at 6 months after recovery from COVID-19, and it showed a link between gut long hauler microbiome dysbiosis and PACS. Specific gut microbiome composition was associated with the presence of PACS. Additionally, certain bacteria were associated with each of the different categories of symptoms in PACS, thus suggesting that different gut communities may contribute to the different PACS symptoms.

The weaknesses of this study were that it was in a relatively small cohort, and that diet and lifestyle were not taken into account. However, since we know that the status of the gut has far-reaching consequences away from the gut as well as in it, it is not surprising that continued dysbiosis in PACS sufferers 6 months post-recovery, but not in patients without PACS, occurred.

The 2022 study suggested that stool analysis may be a way to predict who will become a long hauler. If you are a long hauler (or want to gain information that may help you stay healthier) and wish to know if the current state of your gut is in dysbiosis and what you can do to improve gut microbiota composition, I offer a stool test and one-time consultation package. Please contact me for more details.

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