You beardie walks around and you will never get all the bacteria. Using proper "hygene" for your cage means disinfecting. You shouldn't put sand in and just scoop out the poo and put more sand in when it gets low. You should replace the sand. Again, I use sand in select areas, not the entire enclosure. He has never pooped in his den just on the tile. I use slate tiles that I have sealed with a nature stone anti-fungal anit-bacterial type sealant. It is non-toxic unless of course you ingest large portions.
Again, there is no perfect substrate. And not to get into an arguement, but a tile floor in my house can just be wiped up, but I still disinfect it once a week. You have to maintain what ever substrate you use. This is not a place and forget, and it should not be an attempt to fing what is easiest for you. We as care takers should look to provide as close to the natural habit as possible. That's not to say a captive bred beardie should only have rocks and sticks and dirt, but needs to have a place to climb and bask, have UV lighting to simulate the sun, as we all stress so much, and have a place they can feel protected, a den. They don't know that a shoe box or a cool natural looking background is what they beed to hide they just know they need a place to hide.
Nick