Alternative Staining Method for Four Parasites that are Difficult to Identify through Direct Inspection.

OBJECTIVE: The aim of the present study was to identify Blastocystis spp. (particularly the granular form), Dientamoeba fragilis, and Entamoeba histolytica/dispar trophozoites, which are difficult to identify using wet mount, as well as Giardia intestinalis cysts, which are difficult to identify by unexperienced researchers, in fresh fecal samples within 5 min using a different fixative employing trichrome staining.

METHODS: The slides were fixed by fixatives based ethyl alcohol, formalin, acetic acid, and distilled water including four different mordants (divalent or polyvalent metals that form coordination complex with some dyes) consisted of zinc sulfate hydrate, copper sulfate hydrate, aluminum sulfate hydrate, and ferric sulfate hydrate using a modification of Gomori's trichrome staining. Samples fixed by Schaudinn fixative including mercury chloride were stained using Wheatley modification of Gomori's trichrome staining as gold standard for control and comparison.

RESULTS: Regarding D. fragilis and E. histolytica/dispar trophozoites, similar results were obtained among the slides stained by classical fixation/staining method and those stained by the alternative method. However, regarding Blastocystis spp. and Giardia intestinalis cysts, classical fixation/staining method was relatively superior to the alternative method.

CONCLUSION: Although the alternative method is slightly inferior to the classical fixation/staining method, it seems to be a good option with respect to the process time.