How many acid fast organisms are there?

Not known

It is impossible to provide an exact answer to this question.  The main idea is that acid-fast organisms are difficult to characterize using standard microbiological techniques.  Keep in mind the fact that acid-fastness is a physical property of certain bacteria to resist to decolorization by acids during staining procedures.  Not too many people know the fact that acid-fast bacteria can be visualized by fluorescence microscopy using specific fluorescent dyes.  It is interesting to know that the most popular technique used to identify acid-fast bacteria is the Ziehl-Neelsen stain.