Case report: Nitazoxanide treatment failure in chronic isosporiasis

We report a 60-year-old immunocompetent patient with chronic biliary isospo riasis who failed to respond to orally administered cotrimoxazole prophylax is and orally administered treatment with nitazoxanide, a 5-nitrothiazole b enzamide compound. Severe malabsorption was regarded as responsible for the subtherapeutic levels of nitazoxanide in plasma and bile, resulting in tre atment failure. Intravenously administered cotrimoxazole stopped the sheddi ng of Isospora belli oocysts in bile within 5 days, excluding initially sus pected resistance to cotrimoxazole. Patients with malabsorption and cholang itis due to Coccidia such as Isospora belli and Cryptosporidium spp. or due to protozoa that cause microsporidiasis seem to be predisposed to fail to respond to otherwise effective treatment.