I've had Eco Earth which is the same stuff mold on me before and get on the wood too. I ended up throwing everything out and chlorhexadine the whole cage and then I switched to aspen. You can achieve the same humidity with aspen or at least I do and as long as your snake doesn't spill the water dish, you should be fine with no mold as the aspen doesn't get wet. A mouth culture is the same thing as a sensitivity test where I am from. Basically they just take the culture and then grow it and find what bacteria or virus it is and then they will know what antibiotic it is sensitive to. Like for my bearded dragon, the culture came back as enterobacter which the vet said is pretty common and is on pretty much anything including dirt. Usually an animals immune system will fight it off but if it becomes stressed or anything that causes the immune system to become compromised, it takes hold. Baytril is a wide spectrum antibiotic but make sure you get the culture because if its viral, baytril wont work on that. My advice though is go to any farm or feed store and ask them for chlorhexadine or the name brand novalsan and follow the directions for mixing. That's the same stuff vets use to disinfect exam rooms. I mix 2 capfuls to 1 gallon of water and then use that to wipe down cages, tables, use it on my hands as a rinse, on utensils. Pretty much anything in my reptile room. But I would use that to wipe down your cage. RI can take awhile to completely clear up. My beardie dealt with it for about 2 months and 2 treatments of Baytril before she completely cleared up. Also raise the cage temp a few degrees to help boost the immune system and also it will make the Baytril work better. Good luck, RI is such a pain especially if its your first time dealing with it as it was for my beardie.