Intensity of infection in AIDS-related intestinal microsporidiosis.

To quantify intensity of infection in AIDS-related microsporidiosis, 20 patients with known microsporidiosis submitted stools for quantitative spore counts after staining with a calcofluor white stain. Nine patients collected stools for 24 h, for assessment of daily spore excretion, stool-to-stool variation in spore excretion, and patient-to-patient variation in intensity of infection. The number of organisms seen in small bowel biopsy specimens from 7 patients was compared with quantitative fecal spore excretion. Fecal spore concentration in 20 patients ranged from 4.5x105 to 4.4x108 spores/mL of stool. There was a strong correlation between fecal spore excretion and duodenal biopsy spore counts (r=.82; P<.024). Microsporidium infections in AIDS patients can be quantified by counting spores in stool and by small bowel biopsy. Variations in intensity of infection from patient to patient are great and are similar to those in AIDS-related Cryptosporidium infection.