It is a serious, well-designed study, with validation in animal models and in additional cohorts of patients with multiple sclerosis (MS). Therefore, the results are solid, although they always need to be extended to multiple populations and countries, because the microbiota changes a lot with diet, ethnicity and lifestyles.

There have already been multiple studies of microbiota in multiple sclerosis and there is a consensus that it is altered in autoimmune diseases such as MS. However, there is still no consensus on which alteration is the most relevant and related to the development of MS, given that each study identifies a species of bacteria as the most relevant. The implication would be that if the species of bacteria that predispose to MS are definitively identified, treatments with antibiotics, intestinal flora and even diet could be used to prevent it or improve its clinical course.

[Regarding possible limitations] Validation in large patient populations in multiple countries will be necessary for the results to be robust. The relationship of these results to the genotype of each MS patient and their relationship to latent Epstein-Barr virus infection remains to be established.

The study uses an appropriate methodology and is a good example of how we can advance our understanding of the relationship between microbiota and disease by combining comparative patient-control studies with the use of animal models that can be manipulated to test different hypotheses.

The work provides interesting results and points to possible relationships between the abundance of certain bacteria and the severity of the disease, which could have clinical applications with new diagnostic methods.

It studies a small cohort from a single population and other studies would have to validate these results in other populations and with more samples. The results in humans point to quite complex relationships that differ somewhat from the results in mice. For example, Akkermansia does not appear among the species with the greatest differences in patient-control comparisons, but it does appear in mice, which could indicate important differences between the animal model and the situation in humans. The study focuses on the possible role of a few species, which possibly simplifies a more complex reality as suggested by the great variability observed.