In VitroAntimicrobial Susceptibility Patterns of Blastocystis

ABSTRACTBlastocystisis the most common human enteric protist with controversial clinical significance. Metronidazole is considered a first-line treatment forBlastocystisinfection; however, there has been increasing evidence for the lack of efficacy of this treatment. Treatment failure has been reported in several clinical cases, and recentin vitrostudies have suggested the occurrence of metronidazole-resistant strains. In this study, we tested 12Blastocystisisolates from 4 commonBlastocystissubtypes (ST1, ST3, ST4, and ST8) against 12 commonly used antimicrobials (metronidazole, paromomycin, ornidazole, albendazole, ivermectin, trimethoprim-sulfamethoxazole [TMP-SMX], furazolidone, nitazoxanide, secnidazole, fluconazole, nystatin, and itraconazole) at 10 different concentrationsin vitro. It was found that each subtype showed little sensitivity to the commonly used metronidazole, paromomycin, and triple therapy (furazolidone, nitazoxanide, and secnidazole). This study highlights the efficacy of other potential drug treatments, including trimethoprim-sulfamethoxazole and ivermectin, and suggests that current treatment regimens be revised.