At my hospital (900+ bed), we do acid fast stains on gastric specimens.
They is no way that you will get false positives. The organisms that you
are looking for are bacilli and if you use fluorochrome dyes such as
auramine and rhodamine with a potassium permanganate counterstain, you
will not get false positives. "Normal" bacteria such as Staph aureus do
not stain and will not stain. Also, using a partial acid fast stain
procedure using Carbolfuschin will also not provide false positives
because the organisms are special and are coated with a thick, waxy
material that resists staining; however, once stained, the bacteria will
resist decolorization by strong solvents such as acid alcohol used in the
fluorochrome stains. Normal bacteria do not resist staining and will
over-decolorize...
jen
