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Microbes & Immunity Microbial involvement in ME/CFS

manifestations of ME/CFS. In addition, both genetic (e.g., Coxiella burnetti) and mainly viral (e.g., Epstein-Barr,
5,76
and environmental factors can affect the gut microbiome, Ross River, SARS-CoV-2), in triggering this disease. 82-84
and shifts in local gut microbiota composition should The recent pandemic of COVID-19 caused a serious
be evaluated in ME/CFS. Although the significance of impairment in quality of life and led to long COVID-19
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the gut microbiome in health and disease is becoming in numerous patients who “recovered” but did not return
increasingly clear, limitations must be addressed to full health. In this regard, long COVID-19 shares
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regarding studies of the gut microbiota and ME/CFS, many phenotypic abnormalities with ME/CFS following
such as differing results, small sample sizes, confounding viral infections, including persistent chronic fatigue and
variables, and lack of homogeneity of the microbial gene myalgia.
sequencing platforms. 45,55
Butyrate and its precursor acetate are two of the most 6. Conclusion
important SCFAs of microbial origin. Both metabolites Research on patients with ME/CFS has revealed variable
are reduced in ME/CFS patients likely due to the decrease findings on alterations in gastrointestinal processes that
of F. prausnitzii, Ruminococcus spp., Eubacterium rectale, involve microbiota. Microbiome changes or metabolic
and C. secundus in their gut microbiome (Table 1). Thus, endotoxemia may be potential biomarkers of ME/CFS. The
a deficiency of these intestinal homeostatic metabolites progression of ME/CFS may begin with the loss of beneficial
could contribute to a number of detrimental physiological gut microorganisms, especially SCFA producers that are
perturbations, including a weakened epithelial barrier reflected in plasma metabolite levels. These alterations may
and increased intestinal inflammation, which results result in metabolic and phenotypic shifts and in ME/CFS.
in elevated plasma LPS levels in ME/CFS, indicative of Randomized controlled trials in well-identified patients
microbial translocation. In addition, F. prausnitzii and with ME/CFS, using diet, FMT, and other approaches may
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Lachnospira (formerly Lactobacillus) rogosae are the major benefit these patients and establish causality.
bacterial species associated with the symptoms of ME/CFS
and with individual and total Multidimensional Fatigue Acknowledgments
Inventory (MFI) scores. 45 None.
The cognitive problems detected in ME/CFS subjects
could be related to alterations in the gut microbiota and also Funding
to a substantial decrease in Vitamin E levels. Tryptophan, None.
a precursor for serotonin, can be degraded by determined
gut microorganisms, which may exert influence on brain Conflict of interest
function, and on the pathophysiology of ME/CFS. Thus,
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studying the changes in gut microbiome composition and The authors declare that they do not have competing
function may clarify how tryptophan metabolism affects interests.
serotonin concentrations, which may contribute to various Author contributions
symptoms of ME/CFS, such as depression and restless sleep.
Conceptualization: Alejandro Borrego-Ruiz
Considering the impact of ME/CFS on mental health,
the exploration of psychobiotics as a therapeutic option Writing – original draft: Juan J. Borrego
Writing – review & editing: Alejandro Borrego-Ruiz
for patients with ME/CFS holds considerable promise.
Psychobiotics, which target the gut-brain axis, have Ethics approval and consent to participate
demonstrated potential in modulating anxiety, depression,
and stress-related disorders through gut microbiome Not applicable.
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adjustments. Diet also offers possibilities for ME/CFS
symptom management. Specifically, vegetarian diets, rich Consent for publication
in antioxidant and fiber, are known to enhance gut health, Not applicable.
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lower inflammatory markers, and reduce oxidative stress,
which may be beneficial to mitigate the physiological Availability of data
responses commonly reported by patients with ME/CFS. Not applicable.
In addition, vegetarian diets may exert a positive influence
on mental health. 81 References
Another interesting aspect related to ME/CFS is to 1. Nacul L, Authier FJ, Scheibenbogen C, et al. European
delineate the role of microbial infections, both bacterial network on myalgic encephalomyelitis/chronic fatigue

Volume 2 Issue 1 (2025) 22 doi: 10.36922/mi.4783