In your bathroom, there will always be some moisture. There are too many sources of water to completely control them all. You have water coming from condensation, from wet towels, possibly from a leaking pipe and steam from when you run hot water. With all of this water, there is a high likelihood that you mold could start growing in your bathroom. What can you do to prevent it? There is no way to keep mold spores away. They are basically in the air everywhere, but you can do your best to keep them from finding a good place to grow in your bathroom.
If you have any leaky pipes, you should immediately fix the problem. This might require the help of a plumber unless you’re somewhat handy yourself.
You should also avoid letting wet clothes or towels sit in a pile for a long amount of time. It might be necessary to get them out of the bathroom and hang them somewhere to dry.
It is also very important to have good ventilation in your bathroom. If possible, open up a window to get some airflow, but if not, make sure your bathroom ceiling fan is functioning.