Recently, scientists have begun to focus on the hidden yet extensive world of microbes that live in our bodies (the ‘microbiome’ ) and, in fact, most bacterial cells are located in our gut – about 1.5 kg of bacteria per person. It’s now clear that gut bacteria can influence health in a variety of ways, such as by synthesizing nutrients, inhibiting microbial and viral pathogens, and detoxifying food. But they also contribute to the optimal functioning of the immune system; 70% of all immune cells are located in the gastrointestinal tract, for instance.

Gastrointestinal problems are very common in ME/CFS patients, so it’s at least plausible that some abnormality of gut bacteria could be linked to the development of the illness. In a full-text report, Belgian researchers have used high-throughput gene sequencing to search for different species of bacteria in stool samples of ME/CFS patients from Belgium (18 patients) and Norway (25 patients), and from local healthy people.

Compared with Norwegian controls, Norwegian patients had decreased percentages of some Firmicutes sub-populations (Roseburia, Syntrophococcus, Holdemania, Dialister), a strong 20-fold increase of Lactonifactor, and a 3.8-fold increase of the Bacteroidetes genus Alistipes. Belgian patients showed fewer differences compared with local controls, but Lactonifactor was again strongly increased (45-fold) while Asaccharobacter was decreased.

Scientific study of the relationship between the microbiome and human disease is still rudimentary, so all we and the authors can do is speculate about what these results might mean. Roseburia, for example, are thought to contribute to the production of energy and to protect against gut inflammation, while there is some evidence that increases in Alistipes are also related to gut inflammation (the bacteria were first identified in appendicitis tissue). So, it is certainly possible that these findings are consistent with increased intestinal inflammation. However, whether altered gut microbiota is a reproducible feature in ME/CFS populations, and whether microbiota alterations are involved in causing the illnesses or occur over time as a consequence of disease remain to be determined.

Reference: High-throughput 16S rRNA gene sequencing reveals alterations of intestinal microbiota in myalgic encephalomyelitis/chronic fatigue syndrome patients. Frémont M et al.  Anaerobe 2013; 22: 50-6