Autism linked to decreased microbe diversity in the gut: Study

The race to map and understand the microbial microflora that inhabits our guts is one of the hottest topics and greatest challenges in current research. The suggested links between the microbiota and a whole range of health conditions and wellness measures – including digestion, body weight, immunity, mood, and heart health – are only now beginning to be understood.

Writing in PLoS One​, the research team led by Rosa Krajmalnik-Brown of Arizona State University present findings from the first  comprehensive bacterial analysis focusing on commensal – or beneficial –  bacteria in children with ASD, finding that children with autism had significantly fewer types of gut bacteria and had significantly lower amounts of three critical bacteria, Prevotella​, Coprococcus​, and Veillonellaceae​.

"One of the reasons we started addressing this topic is the fact that autistic children have a lot of GI problems that can last into adulthood,"​ Krajmalnik-Brown said. "Studies have shown that when we manage these problems, their behaviour improves dramatically."​

"We think of Prevotella as a healthy, good thing to have,"​ she added. "We believe that a diverse gut is a healthy gut."​

Significant study​

Commenting on the research, Dr Alex Richardson of University of Oxford - and founder of UK-based charity Food and Behaviour (FAB) Research - suggested that the study is important in confirming that 'distinct abnormalities' of gut microflora are present in children with autistic spectrum disorders. 

"Obviously these latest findings are only correlational, but they need following up,"​ she said.

"Given what we know about the very strong links between the health of the brain, the gut and the immune system, we urgently need more research into their possible implications – particularly for developing new treatment approaches,"​ she said.

"Children with autism often have other health problems that an unhealthy balance of gut flora – and its effects on the immune system – might plausibly help to explain."​

Richardson added that many parents and health professionals already maintain that dietary changes can not only improve the general health of children with autism, but can also have an impact on the autism symptoms - "and there is no question that diet affects the gut microbiome,"​ she added.

Study details​

The research team analysed gut microflora from faecal samples in a cohort of 20 healthy and 20 autistic participants aged between 3 and 16 years using high-throughput method – known as pyrosequencing – which allows  many DNA samples to be combined as well as many sequences per sample to be analysed.

In doing so, Krajmalnik-Brown noted that the new study is the first to approach autism from a different angle, by examining the possible role of commensal gut bacteria.

Analysis of the high-throughput data showed that a lower diversity of gut microbes was positively correlated with the presence of autistic symptoms in the study - detecting significantly decreased microbial diversity in the 20 autistic subjects whose faecal samples were analysed.

Specifically, they found that three bacterial genera—Prevotella,​ ​Coprococcus​ and Veillonellaceae​—were diminished in participants with autism, when compared with samples from non-autistic children.

Krajmalnik-Brown noted that these three bacterial groups represent important strains of carbohydrate-degrading and/or fermenting microbes, and as such could be critical for healthy microbial-gut interactions or play a supportive role for a wide network of different microorganisms in the gut.

The latter may explain the decreased diversity observed in autistic participants, she suggested - adding that the group will use the current results as a guide for new studies for autism aimed at modifying bacterial composition in the gut as a form of treatment.