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Journal of Clinical Microbiology, Jul 1997, 1701-1705, Vol 35, No. 7
H Troll, H Marti and N Weiss
Amoebiasis is caused by two distinct species, a pathogenic form (Entamoeba
histolytica) and a nonpathogenic form (Entamoeba dispar), which are
morphologically identical. Although the distinction between these two
species is of great clinical importance, the methods developed for this
purpose either are very time-consuming or involve laborious procedures for
isolation of the DNA. We report here a simple PCR method starting with
fresh stool specimen that allows for the sensitive and reliable distinction
between E. histolytica and E. dispar. After initial concentration by the
sodium acetate-acetic acid- formalin (SAF) method and digestion with
proteinase K, a 0.88-kb sequence of the multicopy 16S rRNA gene served as a
target for PCR amplification. The method starting with unpreserved
specimens proved to be very sensitive and was not influenced by the quick
exposure to SAF fixative during the initial concentration step. However,
storage in SAF fixative prior to testing resulted in a decreased
sensitivity within 2 days. The detection limit of the method was as low as
one copy of the 16S rRNA gene. No cross-reactivity was observed with other
common intestinal protozoa. Mixed infections involving both E. histolytica
and E. dispar could easily be detected at a ratio of 1:10,000 by agarose
gel electrophoresis or a DNA hybridization immunoassay.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Simple differential detection of Entamoeba histolytica and Entamoeba dispar in fresh stool specimens by sodium acetate-acetic acid-formalin concentration and PCR
Swiss Tropical Institute, Basel, Switzerland.
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