IDDF2024-ABS-0172 A potential intestinal pathogen for autism spectrum disorder: fecal enterotoxigenic bacteroides fragilis

<h3>Background</h3> The gut microbiota is closely associated with autism spectrum disorders (ASD), but the specific microorganism involved is not well understood<i>. Bacteroides fragilis</i> has been implicated in ASD in rodent models, though the evidence is inconclusive. <i>B. fragilis</i> exhibits remarkable genetic diversity and can be categorized into enterotoxigenic <i>B. fragilis</i> (ETBF) or non-toxigenic <i>B. fragilis</i> (NTBF). We aimed to investigate the potential role of <i>B. fragilis</i> in the ASD population. <h3>Methods</h3> Fecal samples were collected from 70 individuals with ASD, 45 individuals with Tic disorder (TD) as disease controls, and 64 healthy controls (HC) for PCR analysis to identify <i>B. fragilis</i> and ETBF. In five ASD children who were ETBF (+) and received fecal microbiota transplantation (FMT) treatment, we compared the ETBF copy number by quantitative PCR before and after FMT. <h3>Results</h3> There was no significant difference in the detection of <i>B. fragilis</i> between the ASD, TD, and HC groups, whereas ETBF was higher in ASD than in TD (21.43% vs. 6.67%, <i>P</i> = 0.0335) and HC (21.43% vs. 7.81%, <i>P</i> = 0.0272) (IDDF2024-ABS-0172 Figure 1. Stacked histogram of B. <i>fragilis</i> and subtype in ASD TD and HC children). Among five ASD children who tested positive for ETBF and received FMT treatment, 80% (4/5) showed a clinical response, a 4.5-point decrease in the CARS-2 score. Four cases had a reduction in their CARS-2 score by 5.5-6.5 and a decrease in ETBF copy number by over 90%. One non-responding case had a 2-point decrease in their CARS-2 score and a 49.88% decrease in ETBF copy number (IDDF2024-ABS-0172 Figure 2. Cars 2 scores and fecal ETBF copy number was reduced after FMT treatment in five ASD children). <h3>Conclusions</h3> The detection rate of ETBF was higher in ASD than in TD and HC children. FMT efficacy was correlated with ETBF, which may be a predictor of FMT efficacy for ASD. ETBF is a potential intestinal pathogen and biomarker for diagnostic and therapeutic targets for ASD.