New microbiome study of autism gut

Ian Lipkin and colleagues at Columbia have just published results showing that half of the children with autism and GI dysfunction whose GI tracts were assayed by biopsy harbor the relatively obscure bacterium, Sutterella. None of the children with GI dysfunction but not autism were positive for this bug. The authors conclude that, “Sutterella is a major component of the microbiota in over half of the children with autism and GI dysfunction”. Previous studies of fecal bacteria found different bacterial species preferentially present in samples from autistic children. The Lipkin study sampled bacteria in biopsied GI epithelium, however. Previous studies also identified Sutterella in samples from Crohn’s disease and ulcerative colitis. However, it is not known whether this bug is a cause or a consequence of such inflammatory bowl disorders. Some normal adults are also positive for this bacterium.

Another important result from this study is the presence of antibodies directed against Sutterella specifically in the circulation of the autism cases. This suggests, but does not prove, that the bug could be causing an infection. Since a defective epithelial barrier has previously been found in some autism GI samples, it is possible that the immune reaction occurred without an actual, proliferating infection. Another interesting question is whether there is a deficit in the composition in the normal, commensal bacterial composition of the gut in autism, and Sutterella simply opportunistically invaded that empty niche. Also important is the question of whether the anti-Sutterella antibodies are causing problems in these children. Such antibodies would presumably not be able to invade the brain, but could possibly bind to peripheral nerves by cross-reacting with an epitope that is shared between the bug and the nerve. This could have an effect on pain or other sensory perceptions. Much speculation, but precious little further information is available at this time. Conclusions are further limited by the lack of such biopsies from controls and autistics without GI problems. This is where animal models become particularly important.