https://www.economist.com/science-and-technology/2019/05/30/more-evidence-that-autism-is-linked-to-gut-bacteria?fsrc=scn/tw/te/bl/ed/moreevidencethatautismislinkedtogutbacteriaautismspectrumdisorder
Restoring the balance
The human study, the latest results of which came out a few weeks ago in Scientific Reports, is being conducted by Rosa Krajmalnik-Brown of Arizona State University and her associates. It was prompted by earlier work in which Dr Krajmalnik-Brown and James Adams, a colleague at Arizona State, sequenced the dna of gut bacteria from 20 autistic children to discover which species were present. They found that the children in their sample were missing hundreds of the thousand-plus bacterial species that colonise a “neurotypical” person’s intestine. One notable absence was Prevotella. This bug, which makes its living by fermenting otherwise-indigestible carbohydrate polymers in dietary fibre, is abundant in the alimentary canals of farmers and hunter-gatherers in places like Africa, rare in western Europeans and Americans, and nearly nonexistent in children with asd.
Their discovery led Dr Krajmalnik-Brown and Dr Adams to the idea that restoring the missing bacteria might alleviate autism’s symptoms. Two years ago they tested a process called microbiota transfer therapy (mtt) on 18 autistic children aged between seven and 16. Of their participants 15 were regarded, according to the Childhood Autism Rating Scale, as having “severe” autism.
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Ten weeks after treatment started the children’s Prevotella levels had multiplied 712-fold. In addition, those of another species, Bifidobacterium, had quadrupled. Bifidobacterium is what is known as a “probiotic” organism—something that acts as a keystone species in the alimentary ecosystem, keeping the mixture of gut bacteria healthy. Now, two years later, although levels of Prevotella have fallen back somewhat, they are still 84 times higher than they were before the experiment started. Levels of Bifidobacterium, meanwhile, have gone up still further—being five times higher than they had been at the beginning of the study. This, says Dr Krajmalnik-Brown, suggests the children’s guts have become healthy environments that can recruit beneficial microbes by themselves.
Crucially, these changes in gut bacteria have translated into behavioural changes. Even 18 weeks after treatment started the children had begun showing reduced symptoms of autism. After two years, only three of them still rated as severe, while eight fell below the diagnostic cut-off point for asdaltogether. These eight thus now count as neurotypical.
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