It's long been known that people in Mexico don't get salmonella nearly as often as visitors do. More than just immunity is probably involved here. It turns out that a recent study in the Journal of Agricultural and Food Chemistry shows that the cilantro in Mexican-style salsa has a chemical, dodecanal, that is more effective in killing salmonella bacteria than the antibiotics doctors prescribe to treat it.
Cilantro is used in a lot of Thai and Hmong cooking as well. I recommend making it a regular part of your diet, whether you like salsa or not.
July 10 update: See the simple chemical structure of dodecanal.