In Defense of Bugs: COVID, The Microbiome, & Your Immune System:
Ever had a doctor tell you that there are more microbes in your body than cells? Well, it’s true and those little bugs are essential to your health. They are concentrated in your gut, on your skin, and any other mucosal environment, including your lung! As a whole, the bacteria, viruses, fungi, and even parasites that makeup the human microbiota actively impact human physiology, both for better and for worse depending on the specific strains that inhabit your gut. One of the most important influences these microbes has is on the human immune system.
Though this is something to consider with any disease – acute or chronic – it is especially interesting now, when the SARS-CoV-2 continues to plague the entire globe. As research about the human microbiome increases, more strains are shown to outcompete various pathogens – if there were strains that could either improve an immune response to COVID-19 or prevent the virus from taking hold it could be a novel, and easy treatment to include.
On the other hand, gastrointestinal symptoms such as diarrhea, nausea, and vomiting are now being included in the symptomatology of COVID-19. Researchers are working to elucidate the potential long-term effects of this infection – is it possible that some of those outcomes could be related to a disruption in the microbiome? Though this concern could be voiced for any infection, especially of a GI nature, pandemics break a lot of ground where research is concerned – if the microbiome is disrupted, and leads to increased risk of long-term problems, there is potential that a specific strain of probiotics could prevent these effects.
So what do we know so far?
The human microbiome is established on the first day of life, making this an aspect that can be important to all age groups when it comes to COVID-19, or any other infection. The critical stages of development that educate the immune system on how to function throughout life rely on the microbiotic composition that is established before the age of three. As we continue to age, that original microbiome is influenced by our environment – what we eat, who we live with, the air we breathe, etc all affects the microbes that in a perfect world, benefit us. The hope is that we’re exposed to good bacteria, more than bad; but also that we are exposed to plenty of variable bacteria, as animal studies on “germ-free” models have shown severe immune deficiency (1).This could be an avenue to explore, as it is becoming more obvious that some are more susceptible to developing COVID symptoms, and severe infection outcomes, compared to others.
As our microbiome is established and maturing, there is a bank of about 1000-1500 bacterial species that we know of that could become part of this important system, but only about 160 strains make up each individual’s unique microbial environment, showing how different we all are in this respect. About 90 percent of these species are shown to be in the Firmicutes and Bacteroidetes phyla, with abnormalities being linked to diseases such as obesity, type II diabetes, hypertension, IBD, etc to name a few. And why is that important here? Obesity, type II diabetes, and hypertension are ALL linked to increased risk of a severe, life-threatening SARS-CoV-2 infection! (1)
On top of that, the gut isn’t the only place the human microbiome in habits, making it’s influence more widespread than one may think. Any mucosal surface can inhabit these microbes, but in regards to COVID-19, one obvious place to explore is the microbiome that inhabits the human lung. One thing to consider that is specific to the lung is that because of its exposure to the external environment, it is much more dynamic and transient when compared to the GI tract – it can change quickly and easily depending on the environment and what we are exposed to (2).
Though less dense than the GI tract, the lung microbiota is actually more diverse – including the same Firmicutes and Bacteroidetes phyla, but also Proteobacteria in high proportions. At the genus level, Prevotella, Veillonella, and Streptococcus organisms predominate. In the case of disease, these proportions change, leading to overgrowth of one species and decline in overall diversity (2).
For example, in asthma patients, there is an increased proportion of Haemophilus, Neisseria, Fusobacterium, and Porphyromonas species. In COPD, Lactobacillus, Fusobacteria, Leptotrichia, and Fusobacterium increase in proportion. When looking closer at risk ratios, those with pulmonary dysbiosis tend to have higher rates of pneumonia, regardless of if the cause is bacterial, viral, or fungal. Considering the major pathogenic factor of COVID-19 is whether or not pneumonia occurs, this increased risk is important to remember.
So what about COVID specifically?
Preliminary studies of the microbiome in COVID-19 patients has shown that both the gastrointestinal and pulmonary microbiota are altered, significantly reducing the bacterial diversity. These patients also have found to have a higher ratio of opportunistic pathogens such as Streptococcus, Rothia, Veillonella, and Actinomyces. A second study had similar results, showing higher amounts of Clostridium hathewayi, Actinomyces viscosus, and Bacteroides nordii.
Looking specifically at patients who had passed from a severe COVID infection, biopsies of lung tissue showed mixed bacterial and fungal overgrowth of opportunistic pathogens. Though more studies are needed to elucidate whether this dysbiosis is a contributing factor or a result of the disease, it is obvious there is significant dysbiosis in SARS-CoV-2 infected patients.
What is hypothesized by these researchers, based on this preliminary research, is that the reduced diversity and effect this has on immune response can alter the risk of developing devere respiratory complications significantly, especially in predisposed individuals. They relate this to the fact that the microbiota itself, when functioning appropriately, can act as a barrier, thereby preventing viral attachment to cells. In addition, previous studies have shown a healthy microbial environment can protect against viral flu infections. Some strains, even protecting against lung injury, even when the virus takes hold (2).
In addition, COVID-19 has shown to have gastrointestinal symptoms that sometimes precede the respiratory issues. Researchers warn that the changes nausea, vomiting, and diarrhea may cause, not just in the gastrointestinal tract, but systemically, could be a contributing factor to the severe inflammatory reaction seen in critically ill patients. This was hypothesized due to the link seen between diarrhea and increased need for ICU care in SARS-CoV-2 positive adults. When intestinal barrier integrity declines, as seen with dysbiosis, the innate and adaptive immune cells are triggered to release cytokines into the circulatory system, resulting in systemic inflammation. That on top of a viral infection from COVID-19 could be enough to trigger the cytokine storm that is seen with the most severe cases, especially those resulting in mortality(3).
Though research into the microbiome is still in it’s early stages, it is becoming obvious that our relationship to the bacteria, viruses, fungi, etc that inhabit us is essential to our physiology, with good and bad connotations. We don’t know a lot, but what we do know indicates how alterations in this important system can have drastic effects on our immune system, inflammatory status, and long term health risk. So, as we continue to find out more and more, especially during the times of COVID-19, the vast and complicated microbiome is definitely something to consider!For more information, visit www.LyfeCheck.com or email support@LyfeCheck.com
- Mary Hall, ND, LAc
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