Gastrointestinal flora and gastrointestinal status in children with autism--comparisons to typical children and correlation with autism severity

Abstract

Background: Children with autism have often been reported to have gastrointestinal problems that are more frequent and more severe than in children from the general population.

Methods: Gastrointestinal flora and gastrointestinal status were assessed from stool samples of 58 children with Autism Spectrum Disorders (ASD) and 39 healthy typical children of similar ages. Stool testing included bacterial and yeast culture tests, lysozyme, lactoferrin, secretory IgA, elastase, digestion markers, short chain fatty acids (SCFA's), pH, and blood presence. Gastrointestinal symptoms were assessed with a modified six-item GI Severity Index (6-GSI) questionnaire, and autistic symptoms were assessed with the Autism Treatment Evaluation Checklist (ATEC).

Results: Gastrointestinal symptoms (assessed by the 6-GSI) were strongly correlated with the severity of autism (assessed by the ATEC), (r = 0.59, p < 0.001). Children with 6-GSI scores above 3 had much higher ATEC Total scores than those with 6-GSI-scores of 3 or lower (81.5 +/- 28 vs. 49.0 +/- 21, p = 0.00002).Children with autism had much lower levels of total short chain fatty acids (-27%, p = 0.00002), including lower levels of acetate, proprionate, and valerate; this difference was greater in the children with autism taking probiotics, but also significant in those not taking probiotics. Children with autism had lower levels of species of Bifidobacter (-43%, p = 0.002) and higher levels of species of Lactobacillus (+100%, p = 0.00002), but similar levels of other bacteria and yeast using standard culture growth-based techniques. Lysozyme was somewhat lower in children with autism (-27%, p = 0.04), possibly associated with probiotic usage. Other markers of digestive function were similar in both groups.

Conclusions: The strong correlation of gastrointestinal symptoms with autism severity indicates that children with more severe autism are likely to have more severe gastrointestinal symptoms and vice versa. It is possible that autism symptoms are exacerbated or even partially due to the underlying gastrointestinal problems. The low level of SCFA's was partly associated with increased probiotic use, and probably partly due to either lower production (less sacchrolytic fermentation by beneficial bacteria and/or lower intake of soluble fiber) and/or greater absorption into the body (due to longer transit time and/or increased gut permeability).

Figure 1

Comparison of SCFA's for the Autism-Probiotic group, the Autism-No-Probiotic group, and the controls. Note that the Valerate data is magnified 10x so that it is visible on the chart. The stars indicate the degree of significance of the result of a t-test comparison of the level of SCFA's in the autism subgroup (Probiotic or No-Probiotic) vs. the controls - * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 2

Comparison of ATEC subscores for the Autism-Low 6-GSI group (few GI problems) and the Autism High 6-GSI group (many GI problems); the stars indicate the significance (*** p < 0.001, ** p < 0.01).

Figure 3

6-Item Gastrointestinal Severity Index (6-GSI) vs. total ATEC score.