This can be as simple as 1c bleach per 1 gallon water.  

Bleach didn't make a dent. 

@Peter GoellerI would spray it with a bleach/water mixture, wipe off excess, let it dry, prime with Kilz, and then paint.

.) - they are just going to throw some bleach into it, re-test until it is negative for EC and total coliforms and say "E. coli?

She said she has used bleach to take care of it but that it keeps coming back. 

I'm reading online that a 50/50 solution of bleach and water will do the trick.

We thoroughly cleaned all the mold with cleaner and bleach, got rid of everything and then primed everything with Kilz primer and repainted the bathroom, along with the rest of the house.

Looking to purchase a rehab and the seller has already remediated a mold issue by using bleach and painting everything with Kilz.

In the past, I've scrubbed it off with mild success, treated it with bleach, pressure washed it.

Mix bleach with water 50% in a pump sprayer and spray the heck out of the dark areas.