Here are a couple of pictures showing the test results of an antimicrobial additive applied to a material.  In this case, the additive is Microban.

The first photo shows the treated sample, where after only 24 hours, the bacteria growth did not form anywhere even near to the material.

You can see in this second photo of the untreated sample how the bacteria growth completely covers the entire sample dish and the material.

Now, imagine this is your desk.  Yuck!  You can stop it by cleaning your desk area regularly, but come on....how many of us actually do it?  According to this test, if you don't clean every 24 hours, Ta-Da!  Bacteria-fest!

Next best thing?  Get protection on the items you handle the most.
Add an antimicrobial keyboard.  Add an antimicrobial mouse.  Add an antimicrobial mousepad.  These are just some examples of how you can stop "feeding the bacteria beast", as it were.