MICROSPORIDIA: Diagnosis

The standard O&P concentration is recommended (500 x g for 10 min) with the concentrate sediment being used for all smears and for the FA procedure. Recommended stains include the modified trichrome stains (Weber Green modified trichrome; Ryan Blue modified trichrome). Stool preparations must be very thin, the staining time is 90 min, and the slide must be examined at X1,000 magnification. Unfortunately, stool material contains a lot of artifacts, many of which will mimic microsporidian spores. If the modified trichrome stains are used for stool specimens, positive control material should be available for comparison. There are other stains available, some including heat and some being combined with modified acid-fast stains. Another approach involves chemofluorescence using optical brightening agents (Calcofluor White, Fungi-Fluor, or Uvitex 2B); these reagents are sensitive, but nonspecific. This is a problem when examining stool specimens; both false positive and false negative results have been seen. Currently, there are no