Salmonella!

[Toothless]

My 3 month old son was diagnosed with Salmonella yesterday, and of course the first thing the doctor said was that Toothless caused it.
Now I know reptiles can carry salmonella, but I'm very careful about my care around him. My older son is not allowed to go into the enclosure and all reptile utensils are kept out of reach. Toothless is not allowed out of the enclosure, I use gloves to handle him, and wash my hands after feeding him.
I'm struggling to find out exactly HOW my son caught this nasty thing, and keep it from happening again. The hospital is running further tests to see what strain it is, which will help us find out where it came from.
He got it sometime last weekend, so I have been trying to determine possible sources. I fed toothless chicken last weekend, but never touched him and washed my hands afterwards but there could still have been some contamination I missed. I also opened a new can of formula that weekend, but I'm hoping it didn't come from that. I didn't eat any chicken, beef or eggs, so doubt it came from those. Are there any other possible sources that I should be looking into. I really don't think it came from the lizard itself and would like to clear his name with the doctors at the hospital.
We should know the exact strain by tomorrow, which will help tremendously.
I appreciate any insight people have. I've never dealt with salmonella before, and my poor guy is pretty sick from it. I want to make sure this doesn't happen again!