Diagnostic Findings [Last Modified: ]
Amebiasis
[Entamoeba histolytica]
Causal Agent Life Cycle Geographic Distribution Clinical Features Laboratory Diagnosis Treatment

Molecular diagnosis

Conventional PCR

In reference diagnosis laboratories, molecular analysis by PCR-based assays is the method of choice for discriminating between the pathogenic species (E. histolytica) and the nonpathogenic species (E. dispar).

Agarose gel for E. histolytica PCR
A

A:  Agarose gel (2%) analysis of a PCR diagnostic test for differentiation between E. histolytica and E. dispar.

  • Lanes 1 - 4: Amplification with the Psp3/Psp51 PCR primer pair specific for E. histolytica.  Diagnostic band size - 876 bp.
  • Lanes 6 - 9: Amplification with the NPsp3/NPsp51 PCR primer pair specific for E. dispar.  Diagnostic band size - 876 bp.
  • Lanes 1 and 6: E. histolytica 200:NIH, zymodeme II (positive control for E. histolytica).
  • Lanes 2 and 7: E. dispar 351:IMMiT, zymodeme I (positive control for E. dispar).
  • Lanes 3 and 8: Specimen from a patient with a liver abscess (positive with E. histolytica primers and negative with E. dispar primers).  E. histolytica 333:IMMiT, zymodeme XIV.
  • Lanes 4 and 9: Specimen from an asymptomatic patient (positive with E. dispar primers and negative with E. histolytica primers).  E. dispar 389:IMMiT, zymodeme I.
  • Lane 5: Molecular base pair standard, 100-bp ladder (from 600 to 1,000 bp).

Figure A contributed by Assist. Prof. Przemyslaw Myjak, Ph.D., Institute of Maritime and Tropical Medicine, Gdynia, Poland.

Real-Time PCR

A TaqMan real-time PCR approach has been validated at CDC and is used for differential laboratory diagnosis of amebiasis.2  The assay targets the 18S rRNA gene with species-specific TaqMan probes in a duplex format, making it possible to detect both species in the same reaction vessel.

Click here to learn more about TaqMan real-time PCR.

References

  1. Clark CG, Diamond LS. Differentiation of pathogenic Entamoeba histolytica from other intestinal protozoa by riboprinting. Arch Med Res 1992;23:15-16.
  2. Qvarnstrom Y, James C, Xayavong M, Holloway B, Moura I, Visvesvara GS, et al. Comparison of real-time PCR rationales for differential laboratory diagnosis of amebiasis. J Clin Microbiol 2005;43:5491-5497.

 
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