I am in mold remediation - and each situation is unique. The first action is to find the reason there is moisture - more than likely you need to install an exhaust fan or make sure there is air moving thru the room for at least 15 minutes after a shower or excess steam accumulates, at least for 15 minutes mold likes moisture and paper, - like drywall, and the binding agent in most paints, and areas that have cabinets, toilets, medicine cabinets etc that are up against the wall with no circulation behind it - moisture gets trapped and its mold for sure. Apply a bleach application to rid the area of mold, there is no magic recipe, ie - to disinfect countertops etc a capful to a gallon of water is sufficient, but if it were me I would probably use 1/4 - 1/2 cup to a gallon, make sure to ventilate the room as you apply it. Let the area dry use a fan if necessary, then you will need to seal it or it can come back, KILZ or ZINSER products work well. Mold is a funny creature, but first realize where the moisture is coming from and fix it - or it happens again and again. Hope this helps.