Myalgic encephalomyelitis (ME), also known as chronic fatigue syndrome (CFS), is a debilitating illness with unclear etiology and no widely accepted therapy. Patients with ME/CFS often report gastrointestinal symptoms. As objective molecular markers for the diagnosis of CFS are lacking, this study examined plasma markers in the microbiota composition of patients with this diagnosis.

Subjects included 48 patients with CFS, and 39 controls who reported good health. For all subjects, fecal and blood samples were collected. From the samples, plasma levels of hsCRP, sCD14, lipopolysaccharade (LPS), LPS binding protein (LBP) and intestinal fatty acid binding protein (I-FABP), and stool for 16S ribosomal ribonucleic acid (rRNA) genes were derived. The levels of hsCRP, lipopolysaccharides (LPS) were measured, as a marker of microbial translocation (MT), and plasma intestinal fatty acid binding protein (I-FABP), as a marker of gastrointestinal damage.

ME/CFS patients had significantly higher plasma levels of LPS, LBP and sCD14 than did controls (P<0.0005), suggesting greater microbial translocation. Based upon data obtained from bacterial 16S rRNA markers, ME/CFS samples were found to have a significantly lower microbial diversity, with lower levels of the genus Faecalbacterium, Bifidobacterium, and the phylum Firmicutes. In addition, increases in proinflammatory species and a reduction in anti-inflammatory species were found in the ME/CSF patients as compared with controls. With data obtained from 16S rRNA and inflammatory markers, individuals were classified correctly as ME/CFS with a cross-validation accuracy of 82.93%.

This study of patients with chronic fatigue syndrome found evidence of ongoing damage to the gut mucosa, and differences between the gut microbiomes of healthy individuals and patients with ME/CFS in the relative abundance of specific genera.