the children in the study took the antibiotic vancomycin for two weeks to remove existing bacteria. then, each of them received a high dose of gut microbes from donors without autism — some children received this as an enema, whereas others took a bacteria-fortified drink. the children continued to take a daily dose of microbes for seven or eight weeks (ethan took his in a shot glass, mixed with cranberry juice), along with an antacid to neutralize stomach acid and improve the chance of the new microbes surviving. at the end of the 18-week study period, the children’s gastrointestinal symptoms had reduced by 80%, and most of the improvement remained two years after the original study. by the two-year mark, the children’s scores on a test to measure how much they were affected by their autism were an average of 47% lower than they had been at the beginning of the trial. also at the two-year follow-up, the children had increased gut-bacterial diversity and greater numbers of gut bacteria that are often found in lower numbers in children with asd, such as bifidobacteria and prevotella. this suggests that the treatment had succeeded in changing their microbiomes long term, krajmalnik-brown says.