You won't like this, but Mythbusters showed that there is faecal matter on your toothbrush even if you keep it in a room other than your toilet/bathroom.
Your mouth, the air, the sink, the walls, your hands etc are all covered in bacteria. The vast vast majority (>99%) are not pathogens, they don't cause illness. But they can still be unpleasant in large numbers of course. But that is actual colonies, not just what you find around the house.
Your toothbrush will be saturated with bacteria, but that isn't really an issue.
Strong alcohol, like vodka or rum will disinfect your toothbrush or a good mouthwash, like listerine.
Or simply, boil the kettle and pour over consistently for about 10-20 seconds. That'll do the job. It's a good idea to that a couple of times over the lifetime of your toothbrush anyway. It helps recover the bristles, and sterilising isn't a bad thing, it's just not necassary.
But it really isn't anything to be concerned about.