The stomach. It is an organ that is home to a whole microbiome of unique strains and types of gut flora – has been an area of great interest for scientists when investigating neural development. Understanding how the brain-gut-enteric microbiota axis influences the behavioural and psychological changes in our body is crucial. It could lead to major breakthroughs in diagnosing and regulating many conditions far more effectively, such as Autism Spectrum Disorder (ASD), which is the focus of this article.

There has been evidence to suggest a strong correlation between the gut flora present and the development of certain neuropathological conditions. For instance, a high proportion of children with ASD suffer with severe gastrointestinal (GI) conditions. Doctors have analysed the stomachs of children who have been diagnosed with ASD. They collected faecal samples from these children. Using fluorescence in situ hybridization and oligonucleotide probes, they detected that the faecal flora of ASD patients had a much higher incidence of Clostridium histolycium bacteria. These motile prokaryotes, normally found in the faeces of rodents, are recognised as toxin-producers. More interestingly, these children with autism were prescribed with oral vancomycin (the conventional method of taking vancomycin is intravenously – this had been specifically done to target gut flora) to see the potential impact of removing neurotoxin producing bacteria. The results showed that once the bacteria were removed, the ASD patients’ symptoms reduced. Once treatment stopped however, the levels of Clostridium histolycium soon increased again, causing regression in treatment for these conditions. This happened due to the persistence of Clostridium histolycium spores.

In this study, a sample size of 58 was sufficient in making these results reliable. In addition to this, a non-autistic sibling group was also included as an effective control to examine the impacts of environmental, lifestyle or genetic factors. It is still unknown what the bacteria produces to affect the brain or how the toxin produced can affect the brain. But it does raise an even more important question. Are the researchers certain that the children have been correctly diagnosed with ASD? Or rather, are they certain that they are dealing with the same type of autism within the widely called umbrella term of ASD?

There have been articles in the past that have proven that symptoms of ASD, such as repetitive behaviour and social seclusion, can be reduced at a young age after treating the child with appropriate antibiotics. The key difference between those articles are the bacteria in question. Clostridium histolycium (the bacteria investigated by the study discussed above) behave very differently in their mannerisms of reproduction and their natural state – they have the ability to reproduce sexually via spores. This is a weird characteristic for a member of the prokaryota domain, but it does explain why the prevalence of ASD in children with a higher incidence of this specific community – the antibiotics or probiotics that most of autistic children take to regulate their GI conditions. Taking supplements to regulate the growth of harmful bacteria in the stomach might help to alleviate symptoms associated with autism, yet there could be, and probably are, bigger factors at play. Even though there appears to be a relationship between gut flora and autism, it is unclear which one causes the other, or whether there is a two interaction.

Bhiramah Rammanohar

Photo Credits due to: