In Vitro Susceptibilities of the Microsporidia Encephalitozoon cuniculi, Encephalitozoon hellem, and Encephalitozoon intestinalis to Albendazole and Its Sulfoxide and Sulfone Metabolites

In vitro comparisons demonstrated that the efficacy of albendazole, albendazole-sulfoxide, and albendazole-sulfone against pathogenic Encephalitozoon species was proportional to the degree of oxidation at a concentration of >10(−3) μg/ml. Furthermore, at a concentration of <10(−2) μg/ml, benzimidazoles were more effective against Encephalitozoon cuniculi and Encephalitozoon hellem than against Encephalitozoon intestinalis.