If you work in the pharmaceutical industry, brush the mold with a swab, touch a culture plate with the swab tip to transfer some of the mold to growth media. Next incubate for several days until a nice healthy cultrure grows. Send it to a lab for identification then contact an appropriate detergent/sanitization vendor for an effective, but pricey solution that will kill the mold but not harm the bottle. True this will cost thousands of dollars, but then you'll KNOW you killed that sucker.

Or you could just throw some bleach in it like I do or buy a new bottle.