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Journal of Clinical Microbiology, Dec 1995, 3138-3145, Vol 33, No. 12
ES Didier, JM Orenstein, A Aldras, D Bertucci, LB Rogers and FA Janney
Calcofluor white 2MR, modified trichrome blue, and indirect
immunofluorescent antibody (IFA) staining methods were evaluated and
compared for detecting microsporidia in stool. Serial 10-fold dilutions of
Encephalitozoon (Septata) intestinalis were prepared in three formalinized
stool specimens or in Tris-buffered saline. Ten-microliter aliquots were
smeared onto glass slides, fixed with methanol, stained, and read by at
least three individuals. The results indicated that the calcofluor stain
was the most sensitive method, required approximately 15 min to perform,
but did generate some false-positive results due to similarly staining
small yeast cells. The modified trichrome blue stain was nearly as
sensitive as the calcofluor stain and allowed for easier distinction
between microsporidia and yeast cells. This stain, however, required
approximately 60 min to perform. The IFA stain with polyclonal murine
antiserum against E. intestinalis was the least sensitive of the methods
and required approximately 130 min to perform. The lower limit of detection
with the calcofluor and modified trichrome stains was a concentration of
about 500 organisms in 10 microliters of stool to detect one microsporidian
after viewing 50 fields at a final magnification of x1,000. Reliability was
also addressed by use of 74 stool, urine, and intestinal fluid specimens,
50 of which were confirmed for the presence of microsporidia by
transmission electron microscopy (TEM). All TEM-positive specimens were
detected by calcofluor and modified trichrome blue staining. Ten specimens
were not detected by the IFA stain. An additional seven TEM-negative
specimens were read positive for microsporidia with the calcofluor stain,
and of these, five also were read positive with the modified trichrome blue
stain. The resulting diagnostic paradigm was to screen specimens with the
calcofluor stain and to confirm the results with the modified trichrome
stain. IFA, which was less sensitive, may become useful for microsporidian
species identification as specific antibodies become available.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Comparison of three staining methods for detecting microsporidia in fluids
Department of Microbiology, Tulane Regional Primate Research Center, Covington, Louisiana 70433, USA. esdid@tpc.tulane.edu
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