>> Wonder if that's why my mom got so sick even though they've been real careful about washing all the produce while they've been living in Mexico. <<
Traveling to *any* different place may make one sick simply because the bacteria are *different* from what one's tummy is used to. That does not necessarily mean *more* bacteria.
Our stumachs *expect* bacteria and even depend on it. However, too much of one kind or something that it is not used to can make tummy go buzzerk.
Traveling and diarreha generally go hand-in-hand.
Just like desk jobs, the human body is not optimized for the Jet Age.