For a new set of keys, I wash them in warm soapy water and then air dry. Then I take paper towel with isopropyl alcohol and rub each keycap. Its not that I don't trust the sender, I don't really trust the manufacturing process. Plus, I'm a biology student so I can get paranoid about small details regarding germs.
Its still not as bad as when I received an old, used model M. Washed them with soap and water, left them in the soap water overnight, then clean with isopropyl alcohol. Repeat three times.