I have a rental house and my tenant moved out unexpectedly. Apparently he never cleaned the tub. Therefore it left black mold in the grout between the wall tiles.

How can I get rid of this? Tile Cleaner seems ineffective. I need a hardcore solution.

In the house we just moved into the grout is uneven in places and actually sticking out past the tiles in some places. is it possible to redo just those areas or do we need to replace all of the grout?