@turquoise-- Hey, I'm not a doctor or anything. But I think that too much gastric juice doesn't directly relate to ulcers. It's the gastric acid in the gastric juice that can do that to you. That's why we take antacids when we have acid problems.
I know that the gastric juice has a specific pH level. If those levels are not suitable to kill a certain bacteria, it might not. But I think it is able to kill most.