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Appl. Environ. Microbiol., Feb 1997, 724-733, Vol 63, No. 2
LJ Anguish and WC Ghiorse
A computer-assisted laser scanning microscope equipped for confocal laser
scanning and color video microscopy was used to examine Cryptosporidium
parvum oocysts in two agricultural soils, a barnyard sediment, and calf
fecal samples. An agar smear technique was developed for enumerating
oocysts in soil and barnyard sediment samples. Enhanced counting efficiency
and sensitivity (detection limit, 5.2 x 10(sup2) oocysts(middot)g [dry
weight](sup-1)) were achieved by using a semiautomatic counting procedure
and confocal laser scanning microscopy to enumerate immunostained oocysts
and fragments of oocysts in the barnyard sediment. An agarose-acridine
orange mounting procedure was developed for high-resolution confocal
optical sectioning of oocysts in soil. Stereo images of serial optical
sections revealed the three-dimensional spatial relationships between
immunostained oocysts and the acridine orange-stained soil matrix material.
In these hydrated, pyrophosphate-dispersed soil preparations, oocysts were
not found to be attached to soil particles. A fluorogenic dye permeability
assay for oocyst viability (A. T. Campbell, L. J. Robertson, and H. V.
Smith, Appl. Environ. Microbiol. 58:3488-3493, 1992) was modified by adding
an immunostaining step after application of the fluorogenic dyes propidium
iodide and 4(prm1),6-diamidino-2-phenylindole. Comparison of conventional
color epifluorescence and differential interference contrast images on one
video monitor with comparable black-and-white laser-scanned confocal images
on a second monitor allowed for efficient location and interpretation of
fluorescently stained oocysts in the soil matrix. This multi-imaging
procedure facilitated the interpretation of the viability assay results by
overcoming the uncertainties caused by matrix interference and background
fluorescence.
Copyright © 1997, American Society for Microbiology
Computer-Assisted Laser Scanning and Video Microscopy for Analysis of Cryptosporidium parvum Oocysts in Soil, Sediment, and Feces
Section of Microbiology, Division of Biological Sciences, Cornell University, Ithaca, New York 14853
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