F10319 FilmTracer™ calcein red-orange biofilm stain is an esterase substrate (calcein red-orange AM) that has utility as a biofilm stain. The stain is non-fluorescent until non-specific esterases hydrolyze the acetoxymethyl ester producing a red orange-fluorecent calcein. This esterase substrate has been shown to be converted by Staphylococcus epidermidis organisms, suggesting that the bacteria are all actively producing esterase.