A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

Winter, 2023 | Number 1, Volume 37

Microbiota therapy may lead to lasting beneficial changes in the gut health of children with ASD

Microbiota transfer therapy (MTT) may lead to long-term improvements in the gut health of children with autism spectrum disorders (ASD), according to a recent study by Khemlal Nirmalkar and colleagues at Arizona State University. 

Interest in MTT as a potential therapy for ASD has been growing due to research indicating that many children with ASD have gastrointestinal (GI) problems such as chronic constipation, diarrhea, and/or abdominal pain. In addition, studies indicate that the gut microbiota of individuals with ASD may differ significantly from the microbiota of neurotypical individuals. Nirmalkar and colleagues note as well that “the gut–brain axis is bidirectional; gut microbiota, metabolic function, and metabolites play an important role in establishing GI and central nervous system (CNS) connections.” 

The researchers’ new study on MTT builds on two earlier studies conducted by their group in 2017 and 2019. In the original study, 18 participants with ASD and GI problems underwent MTT. The researchers found that the treatment reduced gastrointestinal (GI) symptom severity by approximately 80 percent and ASD symptoms by approximately 24 percent, as well as increasing the abundance of several beneficial types of gut bacteria (Bifidobacterium, Prevotella, and Desulfovibrio). A two-year follow-up study of the children showed reductions of approximately 59 percent in GI symptoms and approximately 47 percent in ASD symptoms compared to baseline, and levels of Bifidobacterium, Prevotella, and Desulfovibrio remained higher than at baseline. 

In the new study, the researchers used a technology called “shotgun metagenomics” to obtain detailed data on more than 5,000 bacterial species found in the guts of the children with ASD before and after MTT. They then compared these bacterial populations with those of neurotypical children. 

The researchers found that MTT increased the abundance of beneficial bacteria and also helped to normalize levels of bacterial genes involved in pathways that play roles in folate biosynthesis, sulfur metabolism, and protection against oxidative stress—all processes known to be altered in autism. They note, however, that “over the time (two years) the abundance of Prevotella and Bifidobacterium decreased, which suggests a longer MTT treatment time or a booster after a certain time might be needed for the retention of these bacteria.” 

Nirmalkar comments, “This study highlights altered levels of important bacterial species and metabolic genes in children with autism and improvements after MTT. Our long-term goal is to understand the functional role of the gut microbiome, fill the knowledge gap of the gut-brain axis in autism, and identify therapeutic targets to improve GI health and behavior in children with autism.”


“Shotgun metagenomics study suggests alteration in sulfur metabolism and oxidative stress in children with autism and improvement after microbiota transfer therapy,” Khemlal Nirmalkar, Fatir Qureshi, Dae-Wook Kang, Juergen Hahn, James B. Adams, and Rosa Krajmalnik-Brown, International Journal of Molecular Sciences, November 3, 2022 (free online). Address: Khemlal Nirmalkar, Biodesign Center for Health Through Microbiomes, Arizona State University, Tempe, AZ 85287, [email protected].


 “Study finds microbiota transfer therapy provides long term improvement in gut health in children with autism, ” news release, Richard Harth, Arizona State University, December 14, 2022.


“2-year follow-up study reveals consistent benefits of microbiota transfer therapy in autism and gut symptoms,” Rosa Krajmalnik-Brown, Dae-Wook Kang, Devon Coleman, Elena L. Polard, Juan Maldonado, Sharon McDonoughMeans, J. Gregory Caporaso, and James B. Adams. The researchers’ findings were presented at the Beneficial Microbes Conference on July 10, 2018. 


 “Microbiota Transfer Therapy alters gut ecosystem and improves gastrointestinal and autism symptoms: an open-label study,” Dae-Wook Kang, James B. Adams, Ann C. Gregory, Thomas Borody, Lauren Chittick, Alessio Fasano, Alexander Khoruts, Elizabeth Geis, Juan Maldonado, Sharon McDonough-Means, Elena L. Pollard, Simon Roux, Michael J. Sadowsky, Karen Schwarzberg Lipson, Matthew B. Sullivan, J. Gregory Caporaso, and Rosa Krajmalnik-Brown, Microbiome, January 2017 (free online). Address: Matthew B. Sullivan, mbsulli@ gmail.com