There's no reason to believe that commercially available frozen pinkies carry any infection or disease that would affect your snake, so I wouldn't worry about it. Any supplier selling pet food that made an animal ill, would go out of business very quickly.
Frozen mice will not "infect" your freezer. There has been recent publicity about frozen mice carrying the strain of salmonella that affects humans (if you use search, there's a lengthy thread about it). However, this is the sort of salmonella is also found in human food such as mass-produced poultry and eggs. The usual hygiene precautions will keep you safe - wash your hands after handling, disinfect surfaces that the food has touched, keep the mice wrapped and away from other food during storage (I keep mine in a plastic tub in my freezer) etc.
The main risk to your snakes would be from mice collected from the wild, which have far more chance of health risks that could be transferred to your snake.
