Retired microbiologist and backyard chicken fancier John Ingraham explains that three proteins in the albumen of healthy chickens help eggs resist contamination naturally, http://www.npr.org/templates/story/story.php?storyId=129472951#commentBlock. The NPR Morning Edition story is illustrated with this picture of a nice Silver Laced Wyandotte.
I wasn't aware of these biochemical facts, which hep explain why, although it's possible for any chicken egg to be infected with Salmonella, I've never heard of anyone being sickened by an egg from a backyard flock.
The FDA released its report on the filthy conditions at the farms that are the source of the recent Salmonella outbreak, http://www.npr.org/templates/story/story.php?storyId=129545903. Four to eight feet of manure piled up and spilling out the doors, and the report avoids mentioning the living conditions of the chickens. A poultry veterinarian from the University of Minnesota comments on how he doesn’t see anything to be alarmed about.
This is the industry mentality that makes these deplorable conditions possible, even defensible. As Temple Grandin said in her book, Animals Make Us Human, “Chicken welfare is so poor that I can’t talk only about the core emotions in this chapter. I have to talk about chickens’ physical welfare as well.”