Researchers have found further evidence linking the type of bacteria in the gut to child with autism spectrum disorders (ASD). The study, which reveals a distinct difference in the fecal samples of children with and without ASD, will be presented at the American Society for Microbiology’s annual meeting in Boston, Mass., May 17 to 20.

Researchers trying to uncover the mysteries of ASD, a group of complex brain disorders that vary from difficulty in social interactions, to verbal and nonverbal communication, and repetitive behaviors, according to Autism Speaks, the world’s leading autism science and advocacy organization founded in 2005. Scientists currently believe autism begins very early in childhood brain development; however the first signs aren’t apparent until the child is two-to three-years-old.  With one out of every 68 children identified with autism, it has become an important focal point of research, according to the Centers for Disease and Prevention. Currently, autism research has placed its spotlight on the relationship between specific gut bacteria and the brain.

“We know clearly that many children with autism have GI problems, but we don't know exactly how those GI disturbances are related to brain function,” comments Paul Wang, Autism Speaks vice president for medical research. “We need to understand the interplay between the gut and the brain so that we can identify the right treatment approaches.” 

The newest findings, which will be presented this week, have found increasing evidence that children with autism have a different gut bacteria environment. After researchers at the Biodesign Institute of Arizona State University looked at fecal matter samples from children with and without autism, they found seven of the 50 compounds were significantly different.

"Most of the seven metabolites could play a role in the brain, working as neurotransmitters or controlling neurotransmitter biosynthesis," Kang said . "We suspect that gut microbes may alter levels of neurotransmitter-related metabolites affecting gut-to-brain communication and/or altering brain function."

Children with autism had lower levels of the chemical metabolites, which are produced by certain bacteria. The metabolites homovanillate is the broken down product of dopamine, a major neurotransmitter, while N,N-dimethylglycine is a building block for proteins and neurotransmitters. With both of these gut-produced chemicals at an abnormally low level, researchers conclude the bacteria could be affecting the brain.

Some researchers, such as Dr. Christopher Howerton, from the University of Pennsylvania Medical School’s Center for Research on Reproduction and Women's Health, hypothesized that since our gut microbiome is created based off of our mother’s vaginal microbiome as our baby selves passed through her birthing canal, a change in stress levels could be the reason why the microbes change.

Howerton and colleagues presented their theories and research at Neuroscience 2013, where they described their animal studies’ findings. Stress during pregnancy increased the risk that the animal’s offspring will develop autism-like behaviors and when their microbiome was tested only a few days after birth, there was the same abnormal levels that researchers most recently found in children’s fecal matter.

"Correlations between gut bacteria and neurotransmitter-related metabolites are stepping stones for a better understanding of the crosstalk between gut bacteria and autism, which may provide potential targets for diagnosis or treatment of neurological symptoms in children with ASD," Kang said.