Probiotic-based diet supplementations are among potential treatments of Autism Spectrum Disorders (ASDs) because of the existing gut microbiota profile-mental health. In order to conceive a personalized probiotic supplement to a specified autistic adult, the fecal microbiota of his neurotypical father, mother and sister, have been analyzed and compared. The latest 16S rRNA technology was used for microbial determination at species level (Mymicrozoo analysis, The Netherlands). Less microbiota diversity and an uncommon higher Streptococcus/Lactobacillus abundance ratio were revealed in the autistic adult compared to his relatives. These results were discussed in relation to his digestive issues.