Like Toby said common sense sanitation is the best policy. A alcohol based hand sanitizer used on all areas touched by the WC would be smart. If you want to go overboard I am sure just taking a shower and changing clothes when you get home from work would eliminate all vectors for transferring anything.

Also as Toby said a fecal done by a vet and treatments according to what is found would also be of benefit. Try to avoid any vet that wants to give a "shotgun" medication. They do still exist in the vet world. That would be giving a dewormer and a anti protozoan medication without checking to see what the snake had. Basically give your location and see if anybody has a good vet for your area.

I would hazard a guess that the co-workers might be throwing in WC food items and that should be stopped. A king can eat what it does in the wild because of the temps available in the wild. It can go to the right temps to try and kill off parasites when needed and it can change its diet according to what it "thinks" will be best for it by the condition it is in. In captivity you simply cannot provide all the options that the wild offers so you are restricted to a captive diet of "clean" rodents.

So
1. Sanitation
2. Vet check up
3. Captive diet

Good Luck
Jason