Reduced diversity and altered composition of the gut microbiome in individuals with Myalgic Encephalomyelitis/ChronicFatigue Syndrome

Gastrointestinal disturbances are among the cluster of symptoms commonly reported by individuals diagnosed with ME/CFS (Myalgic Encephalomyelitis/Chronic Fatigue Syndrome), who are also often reported to exhibit altered plasma cytokine profiles. In plasma of ME/CFS patients (n=48) and healthy controls (n=39), we examined a set of inflammatory markers: C-reactive protein (CRP), Intestinal Fatty Acid Binding Protein (I-FABP), lipopolysaccharide (LPS), LPS binding protein (LBP), and soluble CD14 (sCD14). Levels of LPS, LBP, and sCD14 were elevated in ME/CFS subjects. Levels of LBP were correlated with LPS and sCD14 and LPS levels correlated with sCD14. We examined the gut microbiota by 16S rRNA sequencing. We observed that bacterial diversity was decreased in the ME/CFS specimens compared to controls, in particular a reduction in the relative abundance and diversity of Firmicutes. The ME/CFS samples also exhibited an increase in the pro-inflammatory family Enterobacteriaceae and decrease in the anti-inflammatory Ruminococcaceae, including Faecalibacterium, and reduced amounts of beneficial Bifidobacterium species. Using a machine learning approach, individuals were classified correctly as ME/CFS with an average success rate of 0.8928. Our results indicate dysbiosis of the gut microbiota in this disease and further suggest an increased incidence of microbial translocation, which may play a role in inflammatory symptoms.