To prevent mold growth under a bath mat, make sure to keep the mat dry between uses by hanging it up in a well-ventilated area.  Regularly clean the mat with a mild detergent and hot water, and ensure that it dries completely before use. Don't forget to clean the surface underneath the mat with a disinfectant cleaner and let it dry completely before placing the mat back on top.  Consider buying a bath mat that is labeled as \\"mildew-resistant\\" or \\"anti-microbial\\" to inhibit the growth of mold and other microorganisms.