Background/Aims: The pathogenesis of the diarrhea in acquired immunodeficiency syndrome (AIDS)-related cryptosporidiosis is not known. The hypothesis of this study was that the intestinal dysfunction and injury are related to the number of organisms infecting the intestinal mucosa. The aim of this study was to study the influence of intensity of infection on intestinal function and injury in AIDS-related cryptosporidiosis. Methods: In 16 patients with AIDS with intestinal Cryptosporidium infection, the intensity of infection was quantified by counting the total number of fecal oocysts excreted in 24 hours and by determining the percent of duodenal epithelium covered by organisms. Intestinal function was assessed by vitamin B12 absorption and serum d-xylose test. Intestinal injury was assessed by morphology of duodenal mucosa, differential urinary excretion of lactulose and mannitol, and fecal α1-antitrypsin clearance. Measurements were repeated after treatment with paromomycin. Results: Vitamin B12 and d-xylose absorption negatively correlated with intensity of infection. Villus atrophy occurred only in patients with oocyst excretion of >108 oocyst/24 hours. Lactulose/mannitol urinary excretion ratio showed a positive correlation with intensity of infection. Intestinal function and injury improved in patients whose oocyst counts were reduced by treatment with paromomycin. Conclusions: Cryptosporidium infection in patients with AIDS causes malabsorption and intestinal injury in proportion to the number of organisms infecting the intestine.
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