C.O.
C.:
I believe there is a way to seal them - I personally don't know how. I would contact your local Home Depot or Lowe's and ask them - they usually have "how to" classes.
I know you can't "polish" them..but you should be able to use bleach (the hardest disinfectant) or hydrogen pyroxide - and use a different cloth - like terry to clean - ensure you rinse it out after each swipe so you aren't transferring the gunk.....
GOOD LUCK!!!