This article from the Economist is a sort of a round-up of recent work on the medical implications of our gut bacteria, including autism. It has more information that you might use to broaden your search:
A long term antibiotics prescription messed up my gut bacteria, leading to problems with drowsiness and yeast infections. Strong priobiotics (100B+ cells daily) reverse these probems, which return within days when I stop the priobiotics. I can't speak for autism, but I can tell you first hand that gut bacteria do play a role in our health.
http://www.economist.com/node/21560523
A long term antibiotics prescription messed up my gut bacteria, leading to problems with drowsiness and yeast infections. Strong priobiotics (100B+ cells daily) reverse these probems, which return within days when I stop the priobiotics. I can't speak for autism, but I can tell you first hand that gut bacteria do play a role in our health.