Blastocystis hominis: neutral red supravital staining and its application to in vitro drug sensitivity testing

A simple in vitro drug sensitivity testing system for Blastocystis hominis clinical isolates was developed. Application of supravital staining by neutral red allowed quantitative viability assessment. Four xenic cultures, isolated from human sources, were grown in modified monophasic Robinson's medium and tested for sensitivities to nine available drugs. Assessment was done using the cell-count method from air-dried preparations after supravital staining with neutral red. Also, the light absorbence method was evaluated. Trimethoprim, metronidazole, quinacrine, tetracycline, paromomycin, and two new antiprotozoal drugs, nitazoxanide and deacetyl-nitazoxanide, showed cytostatic or cytocidal effects on all or some Blastocystis isolates. Chloroquine and sulphamethoxazole did not demonstrate any effect at the concentrations studied.