I talked to a Mt Healthy rep earlier this spring. What he said, you can take from where it comes. I have no idea if his response was legit or not. But, he said, chickens naturally carry salmonella in their guts. So, birds testing positive is not a big issue... per the rep. Also, Mt. Healthy has had this issue reported before. An other question that needs to be asked and most likely will never be answered is: Is Mt. Healthy simply being reported because they've been caught in the past, and are now under the fire... or is Salmonella much more common in hatchery chicks from lots of companies, but they are slipping by undetected? Now, If I were you, I'd take his statement with a huge grain of salt, given your immuno-compromised status. You might want to talk to your Dr about the situation. It could be that if you exercise normal precautions, such as washing your hands well when handling your chickens, it won't be an issue. After all, we're all exposed to lots of bacteria every day, including the staph that lives on our skin. Or, you could talk to your local vet, and find out how salmonella is normally expressed in avians. Does it show up in the feces? Or elsewhere? Can your birds be tested? Above all else, do what is necessary to take precautions which are reasonable for your situation.