Preheat a grill for high heat.
In a large bowl, mix together the Cheddar cheese, Parmesan cheese, onion, egg, ketchup, and salt.
Crumble in the ground beef, and mix together by hand.
Form into patties, and wrap two slices of bacon around each. Secure bacon with toothpicks.
Place patties on the grill, and cook for 5 minutes per side, or until well done.
Remove toothpicks before serving on hamburger buns.
