Open wide and say “ah”: the new diagnostic test for autism?

A team of Chinese researchers has demonstrated for the first time a link between autism spectrum disorders and changes in the oral flora in children. A simple saliva test could thus be used to diagnose autism.


Should we be armed to the teeth to fight autism? Even though more and more links between intestinal microbiota and autism spectrum disorders (ASD) have been found in studies over the years, few researchers have focused on the role of the oral microbiota.  A team from Shanghai recently addressed this gap: researchers sampled saliva and dental plaque from about a hundred children with ASD aged 7 to 14 and compared their oral microbiota to that of healthy children.

Impaired carbohydrate digestion

One of the significant differences was the overt depletion of Prevotella bacteria in dental plaque of autistic patients. Prevotella is a "friendly" bacterium present in our intestine which helps produce vitamins and digest a certain type of saccharides present in cereals, fruits and vegetables. This observation could partly explain why people with ASD often have intestinal disorders associated with deficiencies in saccharide metabolism.

Harmful bacteria

They also found that pathogenic bacteria were significantly more abundant in children with ASD: more bacteria from the Haemophilus genus, which includes species known to cause meningitis; and also more bacteria from the Streptococcus genus, which are responsible for sore throat and which could be involved in Tourette's syndrome or Parkinson’s disease according to several studies. When the oral microbiota is altered, tooth brushing or chewing could allow these “harmful”  bacteria to be released into the blood flow, later reach the brain and potentially play a role in the disease's progression. And it is interesting to note that children with ASD often have poor oral hygiene, due to a lack of manual dexterity or to difficulties encountered by parents to properly establish hygiene habits.

Could screening tests become available soon?

Finally, this very detailed analysis allowed the researchers to develop a diagnostic tool associated to the severity of autism spectrum disorders, whose efficacy is over 96%. Oral microbiota sampling is more practical and less annoying than stool sampling and it could be used as the first laboratory test for ASD, whose diagnosis is currently based on clinical observations more than scientific tests.



Qiao et al. Alterations of oral microbiota distinguish children with autism spectrum disorders from healthy controls. Scientific reports 2018 ; 8 :1597